Provided by: fio_3.12-2_amd64 bug

NAME

       fio - flexible I/O tester

SYNOPSIS

       fio [options] [jobfile]...

DESCRIPTION

       fio  is a tool that will spawn a number of threads or processes doing a particular type of
       I/O action as specified by the user.  The typical use of  fio  is  to  write  a  job  file
       matching the I/O load one wants to simulate.

OPTIONS

       --debug=type
              Enable  verbose  tracing type of various fio actions. May be `all' for all types or
              individual types separated by a comma (e.g. `--debug=file,mem' will enable file and
              memory debugging). `help' will list all available tracing options.

       --parse-only
              Parse options only, don't start any I/O.

       --merge-blktrace-only
              Merge blktraces only, don't start any I/O.

       --output=filename
              Write output to filename.

       --output-format=format
              Set the reporting format to `normal', `terse', `json', or `json+'. Multiple formats
              can be selected, separate by a comma. `terse' is a CSV  based  format.  `json+'  is
              like `json', except it adds a full dump of the latency buckets.

       --bandwidth-log
              Generate aggregate bandwidth logs.

       --minimal
              Print statistics in a terse, semicolon-delimited format.

       --append-terse
              Print   statistics   in   selected  mode  AND  terse,  semicolon-delimited  format.
              Deprecated, use --output-format instead to select multiple formats.

       --terse-version=version
              Set terse version output format (default `3', or `2', `4', `5').

       --version
              Print version information and exit.

       --help Print a summary of the command line options and exit.

       --cpuclock-test
              Perform test and validation of internal CPU clock.

       --crctest=[test]
              Test the speed of the built-in checksumming functions. If no argument is given, all
              of  them  are tested. Alternatively, a comma separated list can be passed, in which
              case the given ones are tested.

       --cmdhelp=command
              Print help information for command. May be `all' for all commands.

       --enghelp=[ioengine[,command]]
              List all commands defined by  ioengine,  or  print  help  for  command  defined  by
              ioengine. If no ioengine is given, list all available ioengines.

       --showcmd=jobfile
              Convert jobfile to a set of command-line options.

       --readonly
              Turn on safety read-only checks, preventing writes and trims. The --readonly option
              is an extra safety guard to prevent users from accidentally  starting  a  write  or
              trim  workload when that is not desired. Fio will only modify the device under test
              if `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite' is given. This safety net
              can be used as an extra precaution.

       --eta=when
              Specifies  when  real-time  ETA  estimate  should be printed. when may be `always',
              `never' or `auto'. `auto' is the default, it  prints  ETA  when  requested  if  the
              output  is  a  TTY.  `always'  disregards  the  output  type,  and  prints ETA when
              requested. `never' never prints ETA.

       --eta-interval=time
              By default, fio requests client ETA status roughly every second. With this  option,
              the  interval is configurable. Fio imposes a minimum allowed time to avoid flooding
              the console, less than 250 msec is not supported.

       --eta-newline=time
              Force a new line for every time period passed. When the unit is omitted, the  value
              is interpreted in seconds.

       --status-interval=time
              Force  a  full status dump of cumulative (from job start) values at time intervals.
              This option does *not* provide per-period measurements. So values such as bandwidth
              are  running  averages.  When  the  time  unit  is  omitted, time is interpreted in
              seconds. Note that using this option with `--output-format=json' will yield  output
              that  technically isn't valid json, since the output will be collated sets of valid
              json. It will need to be split into valid sets of json after the run.

       --section=name
              Only run specified section name in job file. Multiple sections  can  be  specified.
              The  --section  option  allows one to combine related jobs into one file.  E.g. one
              job file could define light, moderate, and heavy sections. Tell fio to run only the
              "heavy"  section  by  giving  `--section=heavy'  command  line option. One can also
              specify the "write" operations in one section and  "verify"  operation  in  another
              section.  The  --section option only applies to job sections. The reserved *global*
              section is always parsed and used.

       --alloc-size=kb
              Set the internal smalloc pool size to kb in KiB. The --alloc-size switch allows one
              to  use  a  larger  pool  size  for  smalloc.  If running large jobs with randommap
              enabled, fio can run out of memory.  Smalloc is an internal  allocator  for  shared
              structures  from  a  fixed size memory pool and can grow to 16 pools. The pool size
              defaults to 16MiB.  NOTE: While running `.fio_smalloc.*' backing  store  files  are
              visible in `/tmp'.

       --warnings-fatal
              All fio parser warnings are fatal, causing fio to exit with an error.

       --max-jobs=nr
              Set  the  maximum number of threads/processes to support to nr.  NOTE: On Linux, it
              may be necessary to increase the shared-memory limit (`/proc/sys/kernel/shmmax') if
              fio runs into errors while creating jobs.

       --server=args
              Start  a backend server, with args specifying what to listen to.  See CLIENT/SERVER
              section.

       --daemonize=pidfile
              Background a fio server, writing the pid to the given pidfile file.

       --client=hostname
              Instead of running the jobs locally, send and run them on the given hostname or set
              of hostnames. See CLIENT/SERVER section.

       --remote-config=file
              Tell fio server to load this local file.

       --idle-prof=option
              Report CPU idleness. option is one of the following:

                     calibrate
                            Run unit work calibration only and exit.

                     system Show aggregate system idleness and unit work.

                     percpu As system but also show per CPU idleness.

       --inflate-log=log
              Inflate and output compressed log.

       --trigger-file=file
              Execute trigger command when file exists.

       --trigger-timeout=time
              Execute trigger at this time.

       --trigger=command
              Set this command as local trigger.

       --trigger-remote=command
              Set this command as remote trigger.

       --aux-path=path
              Use  the  directory  specified  by  path  for  generated state files instead of the
              current working directory.

JOB FILE FORMAT

       Any parameters following the options will be assumed to be job files, unless they match  a
       job file parameter. Multiple job files can be listed and each job file will be regarded as
       a separate group. Fio will stonewall execution between each group.

       Fio accepts one or more job files describing what it is  supposed  to  do.  The  job  file
       format  is  the  classic  ini file, where the names enclosed in [] brackets define the job
       name. You are free to use any ASCII name you  want,  except  *global*  which  has  special
       meaning.  Following  the  job name is a sequence of zero or more parameters, one per line,
       that define the behavior of the job. If the first character in a line is a ';' or  a  '#',
       the entire line is discarded as a comment.

       A *global* section sets defaults for the jobs described in that file. A job may override a
       *global* section parameter, and a job file may even have several *global* sections  if  so
       desired. A job is only affected by a *global* section residing above it.

       The  --cmdhelp  option also lists all options. If used with an command argument, --cmdhelp
       will detail the given command.

       See the `examples/' directory for  inspiration  on  how  to  write  job  files.  Note  the
       copyright and license requirements currently apply to `examples/' files.

JOB FILE PARAMETERS

       Some parameters take an option of a given type, such as an integer or a string. Anywhere a
       numeric value is required, an arithmetic expression may be used, provided it is surrounded
       by parentheses. Supported operators are:

              addition (+)

              subtraction (-)

              multiplication (*)

              division (/)

              modulus (%)

              exponentiation (^)

       For  time values in expressions, units are microseconds by default. This is different than
       for time values not in expressions (not enclosed in parentheses).

PARAMETER TYPES

       The following parameter types are used.

       str    String. A sequence of alphanumeric characters.

       time   Integer with possible time suffix. Without a unit value is interpreted  as  seconds
              unless  otherwise  specified.  Accepts a suffix of 'd' for days, 'h' for hours, 'm'
              for minutes, 's' for seconds, 'ms'  (or  'msec')  for  milliseconds  and  'us'  (or
              'usec') for microseconds. For example, use 10m for 10 minutes.

       int    Integer.  A  whole number value, which may contain an integer prefix and an integer
              suffix.

                     [*integer prefix*] **number** [*integer suffix*]

              The optional *integer prefix* specifies the number's base. The default is  decimal.
              *0x* specifies hexadecimal.

              The  optional  *integer  suffix*  specifies  the  number's  units,  and includes an
              optional unit prefix and an optional unit. For quantities of data, the default unit
              is  bytes.  For  quantities  of  time, the default unit is seconds unless otherwise
              specified.

              With `kb_base=1000', fio follows international  standards  for  unit  prefixes.  To
              specify  power-of-10  decimal  values  defined in the International System of Units
              (SI):

                     K means kilo (K) or 1000
                     M means mega (M) or 1000**2
                     G means giga (G) or 1000**3
                     T means tera (T) or 1000**4
                     P means peta (P) or 1000**5

              To specify power-of-2 binary values defined in IEC 80000-13:

                     Ki means kibi (Ki) or 1024
                     Mi means mebi (Mi) or 1024**2
                     Gi means gibi (Gi) or 1024**3
                     Ti means tebi (Ti) or 1024**4
                     Pi means pebi (Pi) or 1024**5

              With `kb_base=1024' (the default),  the  unit  prefixes  are  opposite  from  those
              specified  in  the  SI and IEC 80000-13 standards to provide compatibility with old
              scripts. For example, 4k means 4096.

              For quantities of data, an optional unit of 'B' may be included (e.g., 'kB' is  the
              same as 'k').

              The  *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega, not milli).
              'b' and 'B' both mean byte, not bit.

              Examples with `kb_base=1000':

                     4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
                     1 MiB: 1048576, 1m, 1024k
                     1 MB: 1000000, 1mi, 1000ki
                     1 TiB: 1073741824, 1t, 1024m, 1048576k
                     1 TB: 1000000000, 1ti, 1000mi, 1000000ki

              Examples with `kb_base=1024' (default):

                     4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
                     1 MiB: 1048576, 1m, 1024k
                     1 MB: 1000000, 1mi, 1000ki
                     1 TiB: 1073741824, 1t, 1024m, 1048576k
                     1 TB: 1000000000, 1ti, 1000mi, 1000000ki

              To specify times (units are not case sensitive):

                     D means days
                     H means hours
                     M mean minutes
                     s or sec means seconds (default)
                     ms or msec means milliseconds
                     us or usec means microseconds

              If the option accepts an upper and lower range, use a colon ':'  or  minus  '-'  to
              separate  such  values.  See  irange  parameter type.  If the lower value specified
              happens to be larger than the upper value the two values are swapped.

       bool   Boolean. Usually parsed as an integer, however only defined for true and  false  (1
              and 0).

       irange Integer  range  with  suffix.  Allows value range to be given, such as 1024-4096. A
              colon may also be used as the separator, e.g. 1k:4k. If the option allows two  sets
              of  ranges,  they  can be specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also
              see int parameter type.

       float_list
              A list of floating point numbers, separated by a ':' character.

JOB PARAMETERS

       With the above in mind, here follows the complete list of fio job parameters.

   Units
       kb_base=int
              Select the interpretation of unit prefixes in input parameters.

                     1000   Inputs comply with IEC 80000-13 and the International System of Units
                            (SI). Use:

                            - power-of-2 values with IEC prefixes (e.g., KiB)
                            - power-of-10 values with SI prefixes (e.g., kB)

                     1024   Compatibility mode (default). To avoid breaking old scripts:

                            - power-of-2 values with SI prefixes
                            - power-of-10 values with IEC prefixes

              See bs for more details on input parameters.

              Outputs always use correct prefixes. Most outputs include both side-by-side, like:

                     bw=2383.3kB/s (2327.4KiB/s)

              If only one value is reported, then kb_base selects the one to use:

                     1000 -- SI prefixes
                     1024 -- IEC prefixes

       unit_base=int
              Base unit for reporting. Allowed values are:

                     0      Use auto-detection (default).

                     8      Byte based.

                     1      Bit based.

   Job description
       name=str
              ASCII  name  of  the  job. This may be used to override the name printed by fio for
              this job. Otherwise the job name is used. On the command line  this  parameter  has
              the special purpose of also signaling the start of a new job.

       description=str
              Text  description of the job. Doesn't do anything except dump this text description
              when this job is run. It's not parsed.

       loops=int
              Run the specified number of iterations  of  this  job.  Used  to  repeat  the  same
              workload a given number of times. Defaults to 1.

       numjobs=int
              Create  the specified number of clones of this job. Each clone of job is spawned as
              an independent thread or  process.  May  be  used  to  setup  a  larger  number  of
              threads/processes  doing the same thing. Each thread is reported separately; to see
              statistics for all clones as a  whole,  use  group_reporting  in  conjunction  with
              new_group.  See --max-jobs. Default: 1.

   Time related parameters
       runtime=time
              Tell  fio  to  terminate  processing  after the specified period of time. It can be
              quite hard to determine for how long a specified job will run, so this parameter is
              handy to cap the total runtime to a given time. When the unit is omitted, the value
              is interpreted in seconds.

       time_based
              If set, fio will run for the duration of the runtime specified even if the  file(s)
              are  completely read or written. It will simply loop over the same workload as many
              times as the runtime allows.

       startdelay=irange(int)
              Delay the start of job for the specified amount of time. Can be a single value or a
              range.  When given as a range, each thread will choose a value randomly from within
              the range. Value is in seconds if a unit is omitted.

       ramp_time=time
              If set, fio will run the specified workload for this amount of time before  logging
              any  performance  numbers.  Useful  for  letting  performance settle before logging
              results, thus minimizing the runtime required for stable  results.  Note  that  the
              ramp_time  is  considered  lead  in time for a job, thus it will increase the total
              runtime if a special timeout or runtime is specified. When the unit is omitted, the
              value is given in seconds.

       clocksource=str
              Use the given clocksource as the base of timing. The supported options are:

                     gettimeofday
                            gettimeofday(2)

                     clock_gettime
                            clock_gettime(2)

                     cpu    Internal CPU clock source

              cpu  is the preferred clocksource if it is reliable, as it is very fast (and fio is
              heavy on time calls). Fio will automatically use this clocksource if it's supported
              and  considered reliable on the system it is running on, unless another clocksource
              is specifically set. For x86/x86-64 CPUs, this means supporting TSC Invariant.

       gtod_reduce=bool
              Enable all of the gettimeofday(2)  reducing  options  (disable_clat,  disable_slat,
              disable_bw_measurement)  plus  reduce  precision  of the timeout somewhat to really
              shrink the gettimeofday(2) call count. With this option enabled, we only  do  about
              0.4%  of  the  gettimeofday(2)  calls  we  would  have done if all time keeping was
              enabled.

       gtod_cpu=int
              Sometimes it's cheaper to dedicate a single thread of execution to just getting the
              current   time.   Fio   (and   databases,  for  instance)  are  very  intensive  on
              gettimeofday(2) calls. With this option, you  can  set  one  CPU  aside  for  doing
              nothing  but  logging  current  time  to  a  shared memory location. Then the other
              threads/processes that run I/O workloads need only copy that  segment,  instead  of
              entering  the kernel with a gettimeofday(2) call. The CPU set aside for doing these
              time calls will be excluded from other uses. Fio will manually clear  it  from  the
              CPU mask of other jobs.

   Target file/device
       directory=str
              Prefix  filenames  with this directory. Used to place files in a different location
              than `./'. You can specify a number of directories by separating the names  with  a
              ':' character. These directories will be assigned equally distributed to job clones
              created by numjobs as long as they  are  using  generated  filenames.  If  specific
              filename(s)  are  set fio will use the first listed directory, and thereby matching
              the filename semantic (which generates a file for each clone if not specified,  but
              lets all clones use the same file if set).

              See  the  filename  option  for information on how to escape ':' and '\' characters
              within the directory path itself.

              Note: To  control  the  directory  fio  will  use  for  internal  state  files  use
              --aux-path.

       filename=str
              Fio  normally  makes  up  a filename based on the job name, thread number, and file
              number (see filename_format). If you want to share files between threads in  a  job
              or  several  jobs  with  fixed  file  paths, specify a filename for each of them to
              override the default. If the ioengine is file based, you can specify  a  number  of
              files  by  separating  the  names  with a ':' colon. So if you wanted a job to open
              `/dev/sda'  and  `/dev/sdb'   as   the   two   working   files,   you   would   use
              `filename=/dev/sda:/dev/sdb'.   This  also  means  that  whenever  this  option  is
              specified, nrfiles is ignored. The size of regular files specified by  this  option
              will  be  size  divided  by number of files unless an explicit size is specified by
              filesize.

              Each colon and backslash in the wanted path must be escaped with a  '\'  character.
              For   instance,   if   the   path   is  `/dev/dsk/foo@3,0:c'  then  you  would  use
              `filename=/dev/dsk/foo@3,0\:c' and if the path is `F:\filename' then you would  use
              `filename=F\:\\filename'.

              On Windows, disk devices are accessed as `\\.\PhysicalDrive0' for the first device,
              `\\.\PhysicalDrive1' for the second etc.  Note: Windows and FreeBSD  prevent  write
              access to areas of the disk containing in-use data (e.g. filesystems).

              The  filename `-' is a reserved name, meaning *stdin* or *stdout*. Which of the two
              depends on the read/write direction set.

       filename_format=str
              If sharing multiple files between  jobs,  it  is  usually  necessary  to  have  fio
              generate  the  exact names that you want. By default, fio will name a file based on
              the default file format specification of `jobname.jobnumber.filenumber'. With  this
              option,  that  can  be  customized.  Fio  will  recognize and replace the following
              keywords in this string:

                     $jobname
                            The name of the worker thread or process.

                     $jobnum
                            The incremental number of the worker thread or process.

                     $filenum
                            The incremental number of the file for that worker thread or process.

              To have dependent jobs share a set of files, this option can be  set  to  have  fio
              generate   filenames   that   are   shared   between  the  two.  For  instance,  if
              `testfiles.$filenum' is specified,  file  number  4  for  any  job  will  be  named
              `testfiles.4'.  The default of `$jobname.$jobnum.$filenum' will be used if no other
              format specifier is given.

              If you specify a path then the directories will be created up to the main directory
              for  the  file.  So for example if you specify `a/b/c/$jobnum` then the directories
              a/b/c will be created before the file setup  part  of  the  job.   If  you  specify
              directory then the path will be relative that directory, otherwise it is treated as
              the absolute path.

       unique_filename=bool
              To avoid collisions between  networked  clients,  fio  defaults  to  prefixing  any
              generated  filenames  (with  a  directory  specified) with the source of the client
              connecting. To disable this behavior, set this option to 0.

       opendir=str
              Recursively open any files below directory str.

       lockfile=str
              Fio defaults to not locking any files before it does I/O to them. If a file or file
              descriptor  is  shared,  fio  can serialize I/O to that file to make the end result
              consistent. This is usual for emulating real workloads that share files.  The  lock
              modes are:

                     none   No locking. The default.

                     exclusive
                            Only  one  thread  or  process  may  do  I/O at a time, excluding all
                            others.

                     readwrite
                            Read-write locking on the file. Many readers may access the  file  at
                            the same time, but writes get exclusive access.

       nrfiles=int
              Number  of files to use for this job. Defaults to 1. The size of files will be size
              divided by this unless explicit size is specified by filesize.  Files  are  created
              for  each  thread separately, and each file will have a file number within its name
              by default, as explained in filename section.

       openfiles=int
              Number of files to keep open at the same time. Defaults to the same as nrfiles, can
              be set smaller to limit the number simultaneous opens.

       file_service_type=str
              Defines  how fio decides which file from a job to service next. The following types
              are defined:

                     random Choose a file at random.

                     roundrobin
                            Round robin over opened files. This is the default.

                     sequential
                            Finish one file before moving on to  the  next.  Multiple  files  can
                            still be open depending on openfiles.

                     zipf   Use a Zipf distribution to decide what file to access.

                     pareto Use a Pareto distribution to decide what file to access.

                     normal Use a Gaussian (normal) distribution to decide what file to access.

                     gauss  Alias for normal.

              For  random,  roundrobin, and sequential, a postfix can be appended to tell fio how
              many I/Os to issue  before  switching  to  a  new  file.  For  example,  specifying
              `file_service_type=random:8' would cause fio to issue 8 I/Os before selecting a new
              file at random. For the non-uniform distributions, a floating point postfix can  be
              given  to  influence  how the distribution is skewed. See random_distribution for a
              description of how that would work.

       ioscheduler=str
              Attempt to switch the device hosting the file to the specified I/O scheduler before
              running.

       create_serialize=bool
              If  true,  serialize  the  file  creation  for the jobs. This may be handy to avoid
              interleaving of data files, which may greatly depend on  the  filesystem  used  and
              even the number of processors in the system. Default: true.

       create_fsync=bool
              fsync(2) the data file after creation. This is the default.

       create_on_open=bool
              If  true,  don't  pre-create files but allow the job's open() to create a file when
              it's time to do I/O. Default: false -- pre-create all necessary files when the  job
              starts.

       create_only=bool
              If true, fio will only run the setup phase of the job. If files need to be laid out
              or updated on disk, only that will be done --  the  actual  job  contents  are  not
              executed. Default: false.

       allow_file_create=bool
              If  true,  fio is permitted to create files as part of its workload. If this option
              is false, then fio will error out if the files it needs to use don't already exist.
              Default: true.

       allow_mounted_write=bool
              If  this  isn't  set, fio will abort jobs that are destructive (e.g. that write) to
              what appears to be a mounted device or partition. This should help  catch  creating
              inadvertently  destructive  tests, not realizing that the test will destroy data on
              the mounted file system. Note that some platforms don't  allow  writing  against  a
              mounted device regardless of this option. Default: false.

       pre_read=bool
              If  this is given, files will be pre-read into memory before starting the given I/O
              operation. This will also clear the invalidate  flag,  since  it  is  pointless  to
              pre-read  and  then  drop  the  cache. This will only work for I/O engines that are
              seek-able, since they allow you to read the same data multiple times. Thus it  will
              not work on non-seekable I/O engines (e.g. network, splice). Default: false.

       unlink=bool
              Unlink the job files when done. Not the default, as repeated runs of that job would
              then waste time recreating the file set again and again. Default: false.

       unlink_each_loop=bool
              Unlink job files after each iteration or loop. Default: false.

       zonemode=str
              Accepted values are:

                     none   The zonerange, zonesize and zoneskip parameters are ignored.

                     strided
                            I/O  happens  in  a  single  zone  until  zonesize  bytes  have  been
                            transferred.   After  that  number  of  bytes  has  been  transferred
                            processing of the next zone starts.

                     zbd    Zoned block device mode. I/O happens sequentially in each zone,  even
                            if  random I/O has been selected. Random I/O happens across all zones
                            instead of being restricted to a single zone.

       zonerange=int
              Size of a single zone. See also zonesize and zoneskip.

       zonesize=int
              For zonemode=strided, this is the number  of  bytes  to  transfer  before  skipping
              zoneskip bytes. If this parameter is smaller than zonerange then only a fraction of
              each zone with zonerange bytes will be accessed.  If this parameter is larger  than
              zonerange  then  each  zone  will be accessed multiple times before skipping to the
              next zone.

              For zonemode=zbd, this is the size of a single zone.  The  zonerange  parameter  is
              ignored in this mode.

       zoneskip=int
              For zonemode=strided, the number of bytes to skip after zonesize bytes of data have
              been transferred. This parameter must be zero for zonemode=zbd.

       read_beyond_wp=bool
              This parameter applies to zonemode=zbd only.

              Zoned block devices are block devices that consist of multiple zones. Each zone has
              a  type, e.g. conventional or sequential. A conventional zone can be written at any
              offset that is a multiple of the block  size.  Sequential  zones  must  be  written
              sequentially. The position at which a write must occur is called the write pointer.
              A zoned block device can be either drive managed, host managed or host  aware.  For
              host  managed  devices  the  host  must ensure that writes happen sequentially. Fio
              recognizes host managed devices and serializes writes to sequential zones for these
              devices.

              If a read occurs in a sequential zone beyond the write pointer then the zoned block
              device will complete the read without reading any data  from  the  storage  medium.
              Since  such  reads lead to unrealistically high bandwidth and IOPS numbers fio only
              reads beyond the write pointer if explicitly told to do so. Default: false.

       max_open_zones=int
              When running a random write test across an entire drive many  more  zones  will  be
              open  than  in  a typical application workload. Hence this command line option that
              allows to limit the number of open zones. The number of open zones  is  defined  as
              the number of zones to which write commands are issued.

       zone_reset_threshold=float
              A  number between zero and one that indicates the ratio of logical blocks with data
              to the total number of logical blocks in the test above which zones should be reset
              periodically.

       zone_reset_frequency=float
              A  number  between  zero  and  one  that indicates how often a zone reset should be
              issued if the zone reset threshold has been exceeded. A  zone  reset  is  submitted
              after  each  (1  /  zone_reset_frequency)  write  requests.  This  and the previous
              parameter can be used to simulate garbage collection activity.

   I/O type
       direct=bool
              If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that OpenBSD
              and  ZFS  on Solaris don't support direct I/O. On Windows the synchronous ioengines
              don't support direct I/O. Default: false.

       atomic=bool
              If value is true, attempt to use atomic direct I/O. Atomic writes are guaranteed to
              be  stable  once acknowledged by the operating system. Only Linux supports O_ATOMIC
              right now.

       buffered=bool
              If value is true, use buffered I/O. This is the  opposite  of  the  direct  option.
              Defaults to true.

       readwrite=str, rw=str
              Type of I/O pattern. Accepted values are:

                     read   Sequential reads.

                     write  Sequential writes.

                     trim   Sequential  trims  (Linux  block  devices  and SCSI character devices
                            only).

                     randread
                            Random reads.

                     randwrite
                            Random writes.

                     randtrim
                            Random trims (Linux block devices and SCSI character devices only).

                     rw,readwrite
                            Sequential mixed reads and writes.

                     randrw Random mixed reads and writes.

                     trimwrite
                            Sequential trim+write sequences. Blocks will be trimmed  first,  then
                            the same blocks will be written to.

              Fio  defaults  to read if the option is not specified. For the mixed I/O types, the
              default is to split them 50/50. For certain types of I/O the result  may  still  be
              skewed a bit, since the speed may be different.

              It  is  possible to specify the number of I/Os to do before getting a new offset by
              appending `:<nr>' to the end of the string given. For a random read, it would  look
              like  `rw=randread:8'  for  passing in an offset modifier with a value of 8. If the
              suffix is used with a sequential I/O pattern, then the `<nr>' value specified  will
              be  added  to  the  generated  offset  for  each  I/O  turning  sequential I/O into
              sequential I/O with holes.  For instance, using  `rw=write:4k'  will  skip  4k  for
              every write. Also see the rw_sequencer option.

       rw_sequencer=str
              If  an  offset  modifier  is given by appending a number to the `rw=str' line, then
              this option controls how that number  modifies  the  I/O  offset  being  generated.
              Accepted values are:

                     sequential
                            Generate sequential offset.

                     identical
                            Generate the same offset.

              sequential  is  only useful for random I/O, where fio would normally generate a new
              random offset for every I/O. If you append e.g. 8 to randread, you would get a  new
              random  offset  for every 8 I/Os. The result would be a seek for only every 8 I/Os,
              instead of for every I/O. Use `rw=randread:8' to specify that. As sequential I/O is
              already   sequential,   setting  sequential  for  that  would  not  result  in  any
              differences. identical behaves in a similar  fashion,  except  it  sends  the  same
              offset 8 number of times before generating a new offset.

       unified_rw_reporting=bool
              Fio  normally reports statistics on a per data direction basis, meaning that reads,
              writes, and trims are accounted and reported separately. If this option is set  fio
              sums the results and report them as "mixed" instead.

       randrepeat=bool
              Seed  the random number generator used for random I/O patterns in a predictable way
              so the pattern is repeatable across runs. Default: true.

       allrandrepeat=bool
              Seed all random number generators in a predictable way so  results  are  repeatable
              across runs. Default: false.

       randseed=int
              Seed  the  random number generators based on this seed value, to be able to control
              what sequence of output is being generated. If not set, the random sequence depends
              on the randrepeat setting.

       fallocate=str
              Whether pre-allocation is performed when laying down files.  Accepted values are:

                     none   Do not pre-allocate space.

                     native Use  a  platform's  native  pre-allocation call but fall back to none
                            behavior if it fails/is not implemented.

                     posix  Pre-allocate via posix_fallocate(3).

                     keep   Pre-allocate via fallocate(2) with FALLOC_FL_KEEP_SIZE set.

                     0      Backward-compatible alias for none.

                     1      Backward-compatible alias for posix.

              May not be available on all supported platforms. keep is only available  on  Linux.
              If  using  ZFS  on  Solaris this cannot be set to posix because ZFS doesn't support
              pre-allocation. Default: native if any pre-allocation methods are  available,  none
              if not.

       fadvise_hint=str
              Use posix_fadvise(2) or posix_madvise(2) to advise the kernel what I/O patterns are
              likely to be issued. Accepted values are:

                     0      Backwards compatible hint for "no hint".

                     1      Backwards compatible hint for "advise with fio workload  type".  This
                            uses  FADV_RANDOM  for  a  random workload, and FADV_SEQUENTIAL for a
                            sequential workload.

                     sequential
                            Advise using FADV_SEQUENTIAL.

                     random Advise using FADV_RANDOM.

       write_hint=str
              Use fcntl(2) to advise the kernel what life time  to  expect  from  a  write.  Only
              supported on Linux, as of version 4.13. Accepted values are:

                     none   No particular life time associated with this file.

                     short  Data written to this file has a short life time.

                     medium Data written to this file has a medium life time.

                     long   Data written to this file has a long life time.

                     extreme
                            Data written to this file has a very long life time.

              The  values  are  all  relative  to  each  other, and no absolute meaning should be
              associated with them.

       offset=int
              Start I/O at the provided offset in the file, given as either a fixed size in bytes
              or  a percentage. If a percentage is given, the generated offset will be aligned to
              the minimum blocksize or to the value of offset_align if provided. Data before  the
              given offset will not be touched. This effectively caps the file size at `real_size
              - offset'. Can be combined with size to constrain the start and end  range  of  the
              I/O workload.  A percentage can be specified by a number between 1 and 100 followed
              by '%', for example, `offset=20%' to specify 20%.

       offset_align=int
              If set to non-zero value, the byte offset  generated  by  a  percentage  offset  is
              aligned  upwards  to  this value. Defaults to 0 meaning that a percentage offset is
              aligned to the minimum block size.

       offset_increment=int
              If this is provided, then the real offset  becomes  `offset  +  offset_increment  *
              thread_number',  where  the  thread  number  is  a  counter that starts at 0 and is
              incremented for each sub-job (i.e. when numjobs option is specified).  This  option
              is  useful  if  there  are  several jobs which are intended to operate on a file in
              parallel disjoint segments, with even spacing between the starting points.

       number_ios=int
              Fio will normally perform I/Os until it has exhausted the size of the region set by
              size,  or  if it exhaust the allocated time (or hits an error condition). With this
              setting, the range/size can be set independently of the number of I/Os to  perform.
              When  fio  reaches  this number, it will exit normally and report status. Note that
              this does not extend the amount of I/O that will be done, it will only stop fio  if
              this condition is met before other end-of-job criteria.

       fsync=int
              If  writing  to a file, issue an fsync(2) (or its equivalent) of the dirty data for
              every number of blocks given. For example, if you give 32 as a parameter, fio  will
              sync  the  file  after every 32 writes issued. If fio is using non-buffered I/O, we
              may not sync the file. The exception is the sg I/O engine, which  synchronizes  the
              disk  cache  anyway. Defaults to 0, which means fio does not periodically issue and
              wait for a sync to complete. Also see end_fsync and fsync_on_close.

       fdatasync=int
              Like fsync but uses fdatasync(2) to only sync data  and  not  metadata  blocks.  In
              Windows,  FreeBSD,  and DragonFlyBSD there is no fdatasync(2) so this falls back to
              using fsync(2).  Defaults to 0, which means fio does  not  periodically  issue  and
              wait for a data-only sync to complete.

       write_barrier=int
              Make every N-th write a barrier write.

       sync_file_range=str:int
              Use  sync_file_range(2)  for  every  int number of write operations. Fio will track
              range of writes that have happened since the last sync_file_range(2) call. str  can
              currently be one or more of:

                     wait_before
                            SYNC_FILE_RANGE_WAIT_BEFORE

                     write  SYNC_FILE_RANGE_WRITE

                     wait_after
                            SYNC_FILE_RANGE_WRITE_AFTER

              So    if    you    do    `sync_file_range=wait_before,write:8',   fio   would   use
              `SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE' for every 8 writes. Also  see
              the sync_file_range(2) man page. This option is Linux specific.

       overwrite=bool
              If  true, writes to a file will always overwrite existing data. If the file doesn't
              already exist, it will be created before the write phase begins. If the file exists
              and  is  large enough for the specified write phase, nothing will be done. Default:
              false.

       end_fsync=bool
              If true, fsync(2) file contents when a write stage has completed.  Default: false.

       fsync_on_close=bool
              If true, fio will fsync(2) a dirty file on close. This differs  from  end_fsync  in
              that  it  will happen on every file close, not just at the end of the job. Default:
              false.

       rwmixread=int
              Percentage of a mixed workload that should be reads. Default: 50.

       rwmixwrite=int
              Percentage of a mixed workload  that  should  be  writes.  If  both  rwmixread  and
              rwmixwrite  is  given  and  the values do not add up to 100%, the latter of the two
              will be used to override the first. This may interfere with a given  rate  setting,
              if  fio  is  asked to limit reads or writes to a certain rate. If that is the case,
              then the distribution may be skewed. Default: 50.

       random_distribution=str:float[,str:float][,str:float]
              By default, fio will use a completely uniform random  distribution  when  asked  to
              perform  random  I/O.  Sometimes  it is useful to skew the distribution in specific
              ways, ensuring that some parts of the data is more hot than others.   fio  includes
              the following distribution models:

                     random Uniform random distribution

                     zipf   Zipf distribution

                     pareto Pareto distribution

                     normal Normal (Gaussian) distribution

                     zoned  Zoned   random   distribution   zoned_abs   Zoned   absolute   random
                            distribution

              When using a zipf or pareto distribution, an input value is also needed  to  define
              the  access  pattern.  For  zipf,  this  is the `Zipf theta'.  For pareto, it's the
              `Pareto power'. Fio  includes  a  test  program,  fio-genzipf,  that  can  be  used
              visualize  what  the  given  input  values will yield in terms of hit rates. If you
              wanted   to   use   zipf   with   a    `theta'    of    1.2,    you    would    use
              `random_distribution=zipf:1.2'  as  the option. If a non-uniform model is used, fio
              will disable use  of  the  random  map.  For  the  normal  distribution,  a  normal
              (Gaussian) deviation is supplied as a value between 0 and 100.

              For  a  zoned  distribution, fio supports specifying percentages of I/O access that
              should fall within what range of the file or device. For example, given a  criteria
              of:

                     60% of accesses should be to the first 10%
                     30% of accesses should be to the next 20%
                     8% of accesses should be to the next 30%
                     2% of accesses should be to the next 40%

              we  can  define  that through zoning of the random accesses. For the above example,
              the user would do:

                     random_distribution=zoned:60/10:30/20:8/30:2/40

              A zoned_abs distribution works exactly like thezoned, except that it takes absolute
              sizes.  For  example,  let's  say  you  wanted  to  define  access according to the
              following criteria:

                     60% of accesses should be to the first 20G
                     30% of accesses should be to the next 100G
                     10% of accesses should be to the next 500G

              we can define an absolute zoning distribution with:

                     random_distribution=zoned:60/10:30/20:8/30:2/40

              For both zoned and zoned_abs, fio supports defining up to 256 separate zones.

              Similarly to how bssplit works for setting ranges and percentages of  block  sizes.
              Like bssplit, it's possible to specify separate zones for reads, writes, and trims.
              If just one set is given, it'll apply to all of them.

       percentage_random=int[,int][,int]
              For a random workload, set how big a percentage should be random. This defaults  to
              100%,  in which case the workload is fully random. It can be set from anywhere from
              0 to 100. Setting it to 0 would make the workload fully sequential. Any setting  in
              between  will  result  in  a  random mix of sequential and random I/O, at the given
              percentages. Comma-separated values may be specified for reads, writes,  and  trims
              as described in blocksize.

       norandommap
              Normally  fio  will  cover  every  block of the file when doing random I/O. If this
              option is given, fio will just get a new random offset without looking at past  I/O
              history.  This  means  that  some  blocks may not be read or written, and that some
              blocks may be read/written more than once. If this option is used with  verify  and
              multiple   blocksizes  (via  bsrange),  only  intact  blocks  are  verified,  i.e.,
              partially-overwritten blocks are ignored.  With an async  I/O  engine  and  an  I/O
              depth  >  1,  it  is possible for the same block to be overwritten, which can cause
              verification errors.  Either do not use norandommap in this case, or also  use  the
              lfsr random generator.

       softrandommap=bool
              See  norandommap.  If  fio  runs  with the random block map enabled and it fails to
              allocate the map, if this option is set it will continue  without  a  random  block
              map.  As  coverage  will  not  be  as  complete as with random maps, this option is
              disabled by default.

       random_generator=str
              Fio supports the following engines for generating I/O offsets for random I/O:

                     tausworthe
                            Strong 2^88 cycle random number generator.

                     lfsr   Linear feedback shift register generator.

                     tausworthe64
                            Strong 64-bit 2^258 cycle random number generator.

              tausworthe is a strong random number generator, but it  requires  tracking  on  the
              side  if  we  want  to  ensure  that  blocks  are  only  read or written once. lfsr
              guarantees that we never generate  the  same  offset  twice,  and  it's  also  less
              computationally  expensive.  It's  not a true random generator, however, though for
              I/O purposes it's typically good enough. lfsr only works with single  block  sizes,
              not with workloads that use multiple block sizes. If used with such a workload, fio
              may read or write some blocks multiple times.  The  default  value  is  tausworthe,
              unless  the  required  space  exceeds 2^32 blocks. If it does, then tausworthe64 is
              selected automatically.

   Block size
       blocksize=int[,int][,int], bs=int[,int][,int]
              The block size in bytes used for I/O units. Default: 4096. A single  value  applies
              to  reads,  writes,  and  trims. Comma-separated values may be specified for reads,
              writes, and trims. A value not terminated in a comma applies to  subsequent  types.
              Examples:

                     bs=256k        means 256k for reads, writes and trims.
                     bs=8k,32k      means 8k for reads, 32k for writes and trims.
                     bs=8k,32k,     means 8k for reads, 32k for writes, and default for trims.
                     bs=,8k         means default for reads, 8k for writes and trims.
                     bs=,8k,         means  default  for  reads,  8k  for writes, and default for
                     trims.

       blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
              A range of block sizes in bytes for I/O units. The issued I/O unit will always be a
              multiple  of  the minimum size, unless blocksize_unaligned is set.  Comma-separated
              ranges may be specified for reads, writes, and trims  as  described  in  blocksize.
              Example:

                     bsrange=1k-4k,2k-8k

       bssplit=str[,str][,str]
              Sometimes  you  want even finer grained control of the block sizes issued, not just
              an even split between them. This option allows you to weight various  block  sizes,
              so  that you are able to define a specific amount of block sizes issued. The format
              for this option is:

                     bssplit=blocksize/percentage:blocksize/percentage

              for as many block sizes as needed. So if you want to define a workload that has 50%
              64k blocks, 10% 4k blocks, and 40% 32k blocks, you would write:

                     bssplit=4k/10:64k/50:32k/40

              Ordering  does  not  matter.  If the percentage is left blank, fio will fill in the
              remaining values evenly. So a bssplit option like this one:

                     bssplit=4k/50:1k/:32k/

              would have 50% 4k ios, and 25% 1k and 32k ios. The percentages  always  add  up  to
              100, if bssplit is given a range that adds up to more, it will error out.

              Comma-separated  values  may be specified for reads, writes, and trims as described
              in blocksize.

              If you want a workload that has 50% 2k reads and 50% 4k reads, while having 90%  4k
              writes and 10% 8k writes, you would specify:

                     bssplit=2k/50:4k/50,4k/90:8k/10

              Fio supports defining up to 64 different weights for each data direction.

       blocksize_unaligned, bs_unaligned
              If  set,  fio  will  issue I/O units with any size within blocksize_range, not just
              multiples of the minimum size. This typically won't work with direct I/O,  as  that
              normally requires sector alignment.

       bs_is_seq_rand=bool
              If  this  option  is  set, fio will use the normal read,write blocksize settings as
              sequential,random blocksize settings instead. Any random read or write will use the
              WRITE  blocksize  settings,  and  any  sequential  read  or write will use the READ
              blocksize settings.

       blockalign=int[,int][,int], ba=int[,int][,int]
              Boundary to which fio will align random  I/O  units.  Default:  blocksize.  Minimum
              alignment  is typically 512b for using direct I/O, though it usually depends on the
              hardware block size. This option is mutually exclusive with using a random map  for
              files, so it will turn off that option. Comma-separated values may be specified for
              reads, writes, and trims as described in blocksize.

   Buffers and memory
       zero_buffers
              Initialize buffers with all zeros. Default: fill buffers with random data.

       refill_buffers
              If this option is given, fio will refill the  I/O  buffers  on  every  submit.  The
              default  is  to  only fill it at init time and reuse that data. Only makes sense if
              zero_buffers  isn't  specified,  naturally.  If  data  verification   is   enabled,
              refill_buffers is also automatically enabled.

       scramble_buffers=bool
              If  refill_buffers  is  too costly and the target is using data deduplication, then
              setting this option will slightly modify the I/O buffer contents to  defeat  normal
              de-dupe  attempts.  This  is  not  enough  to  defeat more clever block compression
              attempts, but it will stop naive dedupe of blocks. Default: true.

       buffer_compress_percentage=int
              If this is set, then fio will attempt to provide I/O  buffer  content  (on  WRITEs)
              that  compresses to the specified level. Fio does this by providing a mix of random
              data followed by fixed pattern data. The fixed pattern  is  either  zeros,  or  the
              pattern specified by buffer_pattern. If the buffer_pattern option is used, it might
              skew the compression ratio slightly. Setting buffer_compress_percentage to a  value
              other  than  100  will also enable refill_buffers in order to reduce the likelihood
              that adjacent blocks are so similar that they over compress when seen together. See
              buffer_compress_chunk  for  how  to  set  a  finer  or  coarser  granularity of the
              random/fixed data regions. Defaults to unset i.e., buffer data will not  adhere  to
              any compression level.

       buffer_compress_chunk=int
              This  setting  allows  fio  to  manage how big the random/fixed data region is when
              using buffer_compress_percentage. When buffer_compress_chunk is set  to  some  non-
              zero  value  smaller  than  the  block size, fio can repeat the random/fixed region
              throughout the I/O buffer at the specified interval (which particularly useful when
              bigger  block  sizes  are used for a job). When set to 0, fio will use a chunk size
              that matches the block size resulting in a single random/fixed  region  within  the
              I/O  buffer. Defaults to 512. When the unit is omitted, the value is interpreted in
              bytes.

       buffer_pattern=str
              If set, fio will fill the I/O buffers with this pattern or with the contents  of  a
              file.  If  not  set,  the  contents of I/O buffers are defined by the other options
              related to buffer contents. The setting can be any pattern of  bytes,  and  can  be
              prefixed  with  0x  for  hex values. It may also be a string, where the string must
              then be wrapped with "". Or it may also be a filename, where the filename  must  be
              wrapped  with  ''  in which case the file is opened and read. Note that not all the
              file contents will be read if that would cause the buffers  to  overflow.  So,  for
              example:

                     buffer_pattern='filename'
                     or:
                     buffer_pattern="abcd"
                     or:
                     buffer_pattern=-12
                     or:
                     buffer_pattern=0xdeadface

              Also you can combine everything together in any order:

                     buffer_pattern=0xdeadface"abcd"-12'filename'

       dedupe_percentage=int
              If  set, fio will generate this percentage of identical buffers when writing. These
              buffers will be naturally dedupable. The contents of the  buffers  depend  on  what
              other  buffer  compression  settings  have  been  set.  It's  possible  to have the
              individual buffers either fully compressible, or not at all  --  this  option  only
              controls  the  distribution of unique buffers. Setting this option will also enable
              refill_buffers to prevent every buffer being identical.

       invalidate=bool
              Invalidate the buffer/page cache parts of the files to be used  prior  to  starting
              I/O  if  the  platform  and  file  type support it. Defaults to true.  This will be
              ignored if pre_read is also specified for the same job.

       sync=bool
              Use synchronous I/O for buffered writes. For the  majority  of  I/O  engines,  this
              means using O_SYNC. Default: false.

       iomem=str, mem=str
              Fio can use various types of memory as the I/O unit buffer. The allowed values are:

                     malloc Use memory from malloc(3) as the buffers. Default memory type.

                     shm    Use shared memory as the buffers. Allocated through shmget(2).

                     shmhuge
                            Same as shm, but use huge pages as backing.

                     mmap   Use  mmap(2)  to allocate buffers. May either be anonymous memory, or
                            can be file backed if a filename  is  given  after  the  option.  The
                            format is `mem=mmap:/path/to/file'.

                     mmaphuge
                            Use  a memory mapped huge file as the buffer backing. Append filename
                            after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file'.

                     mmapshared
                            Same as mmap, but use a MMAP_SHARED mapping.

                     cudamalloc
                            Use GPU memory as the buffers  for  GPUDirect  RDMA  benchmark.   The
                            ioengine must be rdma.

              The  area  allocated  is  a  function  of  the maximum allowed bs size for the job,
              multiplied by the I/O depth given. Note that for shmhuge and mmaphuge to work,  the
              system must have free huge pages allocated. This can normally be checked and set by
              reading/writing `/proc/sys/vm/nr_hugepages' on a Linux system. Fio assumes  a  huge
              page is 4MiB in size. So to calculate the number of huge pages you need for a given
              job file, add up the I/O depth of all jobs (normally one unless  iodepth  is  used)
              and  multiply by the maximum bs set. Then divide that number by the huge page size.
              You can see the size of the huge pages in `/proc/meminfo'. If  no  huge  pages  are
              allocated  by having a non-zero number in `nr_hugepages', using mmaphuge or shmhuge
              will fail. Also see hugepage-size.

              mmaphuge also needs to have hugetlbfs mounted and the file  location  should  point
              there. So if it's mounted in `/huge', you would use `mem=mmaphuge:/huge/somefile'.

       iomem_align=int, mem_align=int
              This  indicates the memory alignment of the I/O memory buffers. Note that the given
              alignment is applied to the first I/O unit buffer, if using iodepth  the  alignment
              of  the  following  buffers are given by the bs used. In other words, if using a bs
              that is a multiple of the page sized in the system, all buffers will be aligned  to
              this value. If using a bs that is not page aligned, the alignment of subsequent I/O
              memory buffers is the sum of the iomem_align and bs used.

       hugepage-size=int
              Defines the size of a huge page. Must at least be equal to the system setting,  see
              `/proc/meminfo'.  Defaults  to  4MiB.  Should  probably  always  be  a  multiple of
              megabytes, so using `hugepage-size=Xm' is the preferred way to set  this  to  avoid
              setting a non-pow-2 bad value.

       lockmem=int
              Pin the specified amount of memory with mlock(2). Can be used to simulate a smaller
              amount of memory. The amount specified is per worker.

   I/O size
       size=int
              The total size of file I/O for each thread of this job. Fio  will  run  until  this
              many  bytes  has been transferred, unless runtime is limited by other options (such
              as runtime, for instance, or increased/decreased by io_size).  Fio will divide this
              size  between  the available files determined by options such as nrfiles, filename,
              unless filesize is specified by the job. If the result of division happens to be 0,
              the  size  is set to the physical size of the given files or devices if they exist.
              If this option is not specified, fio will use the full size of the given  files  or
              devices. If the files do not exist, size must be given. It is also possible to give
              size as a percentage between 1 and 100. If `size=20%' is given, fio will use 20% of
              the  full  size  of  the  given  files  or devices.  Can be combined with offset to
              constrain the start and end range that I/O will be done within.

       io_size=int, io_limit=int
              Normally fio operates within the region set by size,  which  means  that  the  size
              option  sets both the region and size of I/O to be performed. Sometimes that is not
              what you want. With this option, it is possible to define just the  amount  of  I/O
              that  fio  should  do.  For instance, if size is set to 20GiB and io_size is set to
              5GiB, fio will perform I/O within the first 20GiB but  exit  when  5GiB  have  been
              done.  The opposite is also possible -- if size is set to 20GiB, and io_size is set
              to 40GiB, then fio will do 40GiB of I/O within the 0..20GiB region.

       filesize=irange(int)
              Individual file sizes. May be a range, in which case  fio  will  select  sizes  for
              files  at  random  within  the given range and limited to size in total (if that is
              given). If not given, each created file is the same size.   This  option  overrides
              size  in  terms  of  file  size,  which means this value is used as a fixed size or
              possible range of each file.

       file_append=bool
              Perform I/O after the end of the file. Normally fio will operate within the size of
              a  file.  If this option is set, then fio will append to the file instead. This has
              identical behavior to setting offset to the size of a file. This option is  ignored
              on non-regular files.

       fill_device=bool, fill_fs=bool
              Sets  size to something really large and waits for ENOSPC (no space left on device)
              as the terminating condition. Only makes sense with sequential write.  For  a  read
              workload, the mount point will be filled first then I/O started on the result. This
              option doesn't make sense if operating on a raw device node, since the size of that
              is  already  known  by the file system.  Additionally, writing beyond end-of-device
              will not return ENOSPC there.

   I/O engine
       ioengine=str
              Defines how the job issues I/O to the file. The following types are defined:

                     sync   Basic read(2) or write(2) I/O. lseek(2) is used to position  the  I/O
                            location.  See fsync and fdatasync for syncing write I/Os.

                     psync  Basic  pread(2)  or pwrite(2) I/O. Default on all supported operating
                            systems except for Windows.

                     vsync  Basic readv(2) or writev(2) I/O. Will emulate queuing  by  coalescing
                            adjacent I/Os into a single submission.

                     pvsync Basic preadv(2) or pwritev(2) I/O.

                     pvsync2
                            Basic preadv2(2) or pwritev2(2) I/O.

                     libaio Linux  native  asynchronous  I/O.  Note  that  Linux may only support
                            queued  behavior   with   non-buffered   I/O   (set   `direct=1'   or
                            `buffered=0').  This engine defines engine specific options.

                     posixaio
                            POSIX asynchronous I/O using aio_read(3) and aio_write(3).

                     solarisaio
                            Solaris native asynchronous I/O.

                     windowsaio
                            Windows native asynchronous I/O. Default on Windows.

                     mmap   File  is  memory  mapped  with  mmap(2) and data copied to/from using
                            memcpy(3).

                     splice splice(2) is used to transfer the data and  vmsplice(2)  to  transfer
                            data from user space to the kernel.

                     sg     SCSI  generic  sg  v3  I/O. May either be synchronous using the SG_IO
                            ioctl, or if the target is an sg character device we use read(2)  and
                            write(2)  for  asynchronous  I/O. Requires filename option to specify
                            either  block  or  character  devices.  This  engine  supports   trim
                            operations. The sg engine includes engine specific options.

                     null   Doesn't  transfer  any data, just pretends to. This is mainly used to
                            exercise fio itself and for debugging/testing purposes.

                     net    Transfer over the network to  given  `host:port'.  Depending  on  the
                            protocol  used,  the  hostname, port, listen and filename options are
                            used to specify what sort of connection to make, while  the  protocol
                            option  determines  which  protocol will be used. This engine defines
                            engine specific options.

                     netsplice
                            Like net,  but  uses  splice(2)  and  vmsplice(2)  to  map  data  and
                            send/receive.  This engine defines engine specific options.

                     cpuio  Doesn't  transfer  any  data,  but  burns CPU cycles according to the
                            cpuload and cpuchunks options. Setting cpuload=85 will cause that job
                            to  do  nothing but burn 85% of the CPU. In case of SMP machines, use
                            `numjobs=<nr_of_cpu>' to get desired CPU usage, as the  cpuload  only
                            loads  a  single CPU at the desired rate. A job never finishes unless
                            there is at least one non-cpuio job.

                     guasi  The GUASI I/O engine is the Generic  Userspace  Asynchronous  Syscall
                            Interface        approach        to        async       I/O.       See
                            http://www.xmailserver.org/guasi-lib.html for more info on GUASI.

                     rdma   The  RDMA  I/O   engine   supports   both   RDMA   memory   semantics
                            (RDMA_WRITE/RDMA_READ)  and  channel  semantics  (Send/Recv)  for the
                            InfiniBand, RoCE and iWARP  protocols.  This  engine  defines  engine
                            specific options.

                     falloc I/O  engine  that does regular fallocate to simulate data transfer as
                            fio ioengine.

                            DDIR_READ      does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
                            DIR_WRITE      does fallocate(,mode = 0).
                            DDIR_TRIM                does            fallocate(,mode            =
                            FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).

                     ftruncate
                            I/O  engine  that  sends ftruncate(2) operations in response to write
                            (DDIR_WRITE) events. Each ftruncate issued sets the  file's  size  to
                            the current block offset. blocksize is ignored.

                     e4defrag
                            I/O  engine  that  does  regular EXT4_IOC_MOVE_EXT ioctls to simulate
                            defragment activity in request to DDIR_WRITE event.

                     rados  I/O engine  supporting  direct  access  to  Ceph  Reliable  Autonomic
                            Distributed  Object Store (RADOS) via librados. This ioengine defines
                            engine specific options.

                     rbd    I/O engine supporting direct access to Ceph Rados Block Devices (RBD)
                            via  librbd  without  the  need  to  use  the kernel rbd driver. This
                            ioengine defines engine specific options.

                     http   I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to a
                            WebDAV  or  S3  endpoint.   This  ioengine  defines  engine  specific
                            options.

                            This engine only supports direct IO of iodepth=1; you need  to  scale
                            this  via  numjobs.  blocksize  defines the size of the objects to be
                            created.

                            TRIM is translated to object deletion.

                     gfapi  Using GlusterFS libgfapi sync interface to direct access to GlusterFS
                            volumes  without  having  to  go  through FUSE. This ioengine defines
                            engine specific options.

                     gfapi_async
                            Using  GlusterFS  libgfapi  async  interface  to  direct  access   to
                            GlusterFS  volumes  without  having to go through FUSE. This ioengine
                            defines engine specific options.

                     libhdfs
                            Read and write through Hadoop (HDFS). The filename option is used  to
                            specify  host,port  of  the  hdfs  name-node  to connect. This engine
                            interprets offsets a little differently. In HDFS, files once  created
                            cannot be modified so random writes are not possible. To imitate this
                            the libhdfs engine expects a bunch of small files to be created  over
                            HDFS  and  will  randomly  pick  a file from them based on the offset
                            generated by fio backend (see the example job  file  to  create  such
                            files,  use  `rw=write'  option). Please note, it may be necessary to
                            set environment variables to work with  HDFS/libhdfs  properly.  Each
                            job uses its own connection to HDFS.

                     mtd    Read,  write  and  erase an MTD character device (e.g., `/dev/mtd0').
                            Discards are treated as erases. Depending on  the  underlying  device
                            type,  the  I/O  may  have to go in a certain pattern, e.g., on NAND,
                            writing  sequentially  to  erase   blocks   and   discarding   before
                            overwriting. The trimwrite mode works well for this constraint.

                     pmemblk
                            Read and write using filesystem DAX to a file on a filesystem mounted
                            with DAX on a persistent memory device through  the  PMDK  libpmemblk
                            library.

                     dev-dax
                            Read  and write using device DAX to a persistent memory device (e.g.,
                            /dev/dax0.0) through the PMDK libpmem library.

                     external
                            Prefix to specify loading an external I/O engine object file.  Append
                            the  engine  filename,  e.g.  `ioengine=external:/tmp/foo.o'  to load
                            ioengine `foo.o' in `/tmp'.  The  path  can  be  either  absolute  or
                            relative.  See  `engines/skeleton_external.c'  in  the fio source for
                            details of writing an external I/O engine.

                     filecreate
                            Simply create the files and do no I/O to them.  You still need to set
                            filesize  so  that all the accounting still occurs, but no actual I/O
                            will be done other than creating the file.

                     libpmem
                            Read and write using mmap I/O to a file on a filesystem mounted  with
                            DAX on a persistent memory device through the PMDK libpmem library.

                     ime_psync
                            Synchronous  read and write using DDN's Infinite Memory Engine (IME).
                            This engine is very basic and issues calls to IME whenever an  IO  is
                            queued.

                     ime_psyncv
                            Synchronous  read and write using DDN's Infinite Memory Engine (IME).
                            This engine uses iovecs and will try to stack as much IOs as possible
                            (if the IOs are "contiguous" and the IO depth is not exceeded) before
                            issuing a call to IME.

                     ime_aio
                            Asynchronous read and write using DDN's Infinite Memory Engine (IME).
                            This  engine  will  try  to stack as much IOs as possible by creating
                            requests for  IME.   FIO  will  then  decide  when  to  commit  these
                            requests.

   I/O engine specific parameters
       In addition, there are some parameters which are only valid when a specific ioengine is in
       use. These are used identically to normal parameters, with the caveat that  when  used  on
       the command line, they must come after the ioengine that defines them is selected.

       (libaio)userspace_reap
              Normally,  with  the  libaio engine in use, fio will use the io_getevents(3) system
              call to reap newly returned events. With this flag turned on, the AIO ring will  be
              read directly from user-space to reap events. The reaping mode is only enabled when
              polling for a minimum of 0 events (e.g. when `iodepth_batch_complete=0').

       (pvsync2)hipri
              Set RWF_HIPRI on I/O, indicating to the kernel that it's of  higher  priority  than
              normal.

       (pvsync2)hipri_percentage
              When  hipri  is  set  this  determines  the probability of a pvsync2 I/O being high
              priority. The default is 100%.

       (cpuio)cpuload=int
              Attempt to use the specified percentage of CPU cycles. This is a  mandatory  option
              when using cpuio I/O engine.

       (cpuio)cpuchunks=int
              Split the load into cycles of the given time. In microseconds.

       (cpuio)exit_on_io_done=bool
              Detect when I/O threads are done, then exit.

       (libhdfs)namenode=str
              The hostname or IP address of a HDFS cluster namenode to contact.

       (libhdfs)port
              The listening port of the HFDS cluster namenode.

       (netsplice,net)port
              The TCP or UDP port to bind to or connect to. If this is used with numjobs to spawn
              multiple instances of the same job type, then this will be the starting port number
              since fio will use a range of ports.

       (rdma)port
              The  port  to  use  for RDMA-CM communication. This should be the same value on the
              client and the server side.

       (netsplice,net,rdma)hostname=str
              The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O.  If the job is
              a  TCP  listener or UDP reader, the hostname is not used and must be omitted unless
              it is a valid UDP multicast address.

       (netsplice,net)interface=str
              The IP address of the network interface used to send or receive UDP multicast.

       (netsplice,net)ttl=int
              Time-to-live value for outgoing UDP multicast packets. Default: 1.

       (netsplice,net)nodelay=bool
              Set TCP_NODELAY on TCP connections.

       (netsplice,net)protocol=str, proto=str
              The network protocol to use. Accepted values are:

                     tcp    Transmission control protocol.

                     tcpv6  Transmission control protocol V6.

                     udp    User datagram protocol.

                     udpv6  User datagram protocol V6.

                     unix   UNIX domain socket.

              When the protocol is TCP or UDP, the port must  also  be  given,  as  well  as  the
              hostname  if  the job is a TCP listener or UDP reader. For unix sockets, the normal
              filename option should be used and the port is invalid.

       (netsplice,net)listen
              For TCP network connections, tell fio to listen  for  incoming  connections  rather
              than initiating an outgoing connection. The hostname must be omitted if this option
              is used.

       (netsplice,net)pingpong
              Normally a network writer will just continue writing data,  and  a  network  reader
              will  just  consume packages. If `pingpong=1' is set, a writer will send its normal
              payload to the reader, then wait for the reader to send the same payload back. This
              allows  fio  to  measure network latencies. The submission and completion latencies
              then measure local time spent sending or  receiving,  and  the  completion  latency
              measures  how  long  it  took  for  the other end to receive and send back. For UDP
              multicast traffic `pingpong=1' should only be set for a single reader when multiple
              readers are listening to the same address.

       (netsplice,net)window_size=int
              Set the desired socket buffer size for the connection.

       (netsplice,net)mss=int
              Set the TCP maximum segment size (TCP_MAXSEG).

       (e4defrag)donorname=str
              File will be used as a block donor (swap extents between files).

       (e4defrag)inplace=int
              Configure donor file blocks allocation strategy:

                     0      Default. Preallocate donor's file on init.

                     1      Allocate  space  immediately  inside defragment event, and free right
                            after event.

       (rbd,rados)clustername=str
              Specifies the name of the Ceph cluster.

       (rbd)rbdname=str
              Specifies the name of the RBD.

       (rbd,rados)pool=str
              Specifies the name of the Ceph pool containing RBD or RADOS data.

       (rbd,rados)clientname=str
              Specifies the username (without the 'client.'  prefix)  used  to  access  the  Ceph
              cluster.  If  the  clustername  is  specified,  the  clientname  shall  be the full
              *type.id* string. If no type. prefix is given, fio will add 'client.'  by default.

       (rbd,rados)busy_poll=bool
              Poll store  instead  of  waiting  for  completion.  Usually  this  provides  better
              throughput at cost of higher(up to 100%) CPU utilization.

       (http)http_host=str
              Hostname to connect to. For S3, this could be the bucket name. Default is localhost

       (http)http_user=str
              Username for HTTP authentication.

       (http)http_pass=str
              Password for HTTP authentication.

       (http)https=str
              Whether  to use HTTPS instead of plain HTTP. on enables HTTPS; insecure will enable
              HTTPS, but disable SSL peer verification (use with caution!).  Default is off.

       (http)http_mode=str
              Which HTTP access mode to use: webdav, swift, or s3. Default is webdav.

       (http)http_s3_region=str
              The S3 region/zone to include in the request. Default is us-east-1.

       (http)http_s3_key=str
              The S3 secret key.

       (http)http_s3_keyid=str
              The S3 key/access id.

       (http)http_swift_auth_token=str
              The Swift auth token. See the example configuration file on how to retrieve this.

       (http)http_verbose=int
              Enable verbose requests from libcurl. Useful for  debugging.  1  turns  on  verbose
              logging from libcurl, 2 additionally enables HTTP IO tracing.  Default is 0

       (mtd)skip_bad=bool
              Skip operations against known bad blocks.

       (libhdfs)hdfsdirectory
              libhdfs will create chunk in this HDFS directory.

       (libhdfs)chunk_size
              The size of the chunk to use for each file.

       (rdma)verb=str
              The RDMA verb to use on this side of the RDMA ioengine connection. Valid values are
              write, read, send and recv. These correspond to the  equivalent  RDMA  verbs  (e.g.
              write  =  rdma_write etc.). Note that this only needs to be specified on the client
              side of the connection. See the examples folder.

       (rdma)bindname=str
              The name to use to bind the local RDMA-CM connection to a local RDMA  device.  This
              could  be  a  hostname  or an IPv4 or IPv6 address. On the server side this will be
              passed into the rdma_bind_addr() function and on the client site it will be used in
              the  rdma_resolve_add()  function.  This  can  be  useful when multiple paths exist
              between the client and the server or in certain loopback configurations.

       (sg)readfua=bool
              With readfua option set to 1, read operations include the force unit  access  (fua)
              flag. Default: 0.

       (sg)writefua=bool
              With writefua option set to 1, write operations include the force unit access (fua)
              flag. Default: 0.

       (sg)sg_write_mode=str
              Specify the type of write commands to issue. This option can take three values:

                     write (default)
                            Write opcodes are issued as usual

                     verify Issue WRITE AND VERIFY commands. The BYTCHK bit is  set  to  0.  This
                            directs  the  device  to carry out a medium verification with no data
                            comparison. The writefua option is ignored with this selection.

                     same   Issue WRITE SAME commands. This  transfers  a  single  block  to  the
                            device and writes this same block of data to a contiguous sequence of
                            LBAs beginning at the specified offset. fio's  block  size  parameter
                            specifies  the amount of data written with each command. However, the
                            amount of data actually transferred to the device  is  equal  to  the
                            device's  block  (sector)  size.  For a device with 512 byte sectors,
                            blocksize=8k will write 16 sectors with each command. fio will  still
                            generate 8k of data for each command butonly the first 512 bytes will
                            be used and transferred to the device. The writefua option is ignored
                            with this selection.

   I/O depth
       iodepth=int
              Number  of  I/O  units  to  keep  in  flight against the file. Note that increasing
              iodepth beyond 1 will not affect synchronous ioengines (except  for  small  degrees
              when verify_async is in use). Even async engines may impose OS restrictions causing
              the desired depth not to be achieved. This may happen on Linux  when  using  libaio
              and not setting `direct=1', since buffered I/O is not async on that OS. Keep an eye
              on the I/O depth distribution in the fio output to verify that the  achieved  depth
              is as expected. Default: 1.

       iodepth_batch_submit=int, iodepth_batch=int
              This defines how many pieces of I/O to submit at once. It defaults to 1 which means
              that we submit each I/O as soon as it is available, but can  be  raised  to  submit
              bigger  batches  of  I/O  at  the time. If it is set to 0 the iodepth value will be
              used.

       iodepth_batch_complete_min=int, iodepth_batch_complete=int
              This defines how many pieces of I/O to retrieve at once. It  defaults  to  1  which
              means  that  we'll  ask  for  a  minimum of 1 I/O in the retrieval process from the
              kernel. The I/O retrieval will go on until we hit the limit set by iodepth_low.  If
              this  variable  is set to 0, then fio will always check for completed events before
              queuing more I/O. This helps reduce I/O latency, at  the  cost  of  more  retrieval
              system calls.

       iodepth_batch_complete_max=int
              This  defines  maximum  pieces  of I/O to retrieve at once. This variable should be
              used along with iodepth_batch_complete_min=int variable, specifying  the  range  of
              min  and  max  amount  of  I/O which should be retrieved. By default it is equal to
              iodepth_batch_complete_min value. Example #1:

                     iodepth_batch_complete_min=1
                     iodepth_batch_complete_max=<iodepth>

              which means that we will retrieve at least 1 I/O and  up  to  the  whole  submitted
              queue depth. If none of I/O has been completed yet, we will wait.  Example #2:

                     iodepth_batch_complete_min=0
                     iodepth_batch_complete_max=<iodepth>

              which means that we can retrieve up to the whole submitted queue depth, but if none
              of I/O has been completed yet, we will NOT wait and  immediately  exit  the  system
              call. In this example we simply do polling.

       iodepth_low=int
              The  low  water  mark indicating when to start filling the queue again. Defaults to
              the same as iodepth, meaning that fio will attempt to keep the queue  full  at  all
              times. If iodepth is set to e.g. 16 and iodepth_low is set to 4, then after fio has
              filled the queue of 16 requests, it will let the  depth  drain  down  to  4  before
              starting to fill it again.

       serialize_overlap=bool
              Serialize  in-flight  I/Os  that  might  otherwise cause or suffer from data races.
              When two or more I/Os are submitted simultaneously, there is no guarantee that  the
              I/Os will be processed or completed in the submitted order. Further, if two or more
              of  those  I/Os  are  writes,  any  overlapping  region  between  them  can  become
              indeterminate/undefined  on certain storage. These issues can cause verification to
              fail erratically when at least one of the racing I/Os  is  changing  data  and  the
              overlapping  region  has  a  non-zero  size. Setting serialize_overlap tells fio to
              avoid provoking this behavior by explicitly serializing in-flight I/Os that have  a
              non-zero overlap. Note that setting this option can reduce both performance and the
              iodepth achieved.

              This option only applies to I/Os issued for a single job except when it is  enabled
              along  with  io_submit_mode=offload.  In  offload  mode, fio will check for overlap
              among all I/Os submitted by offload jobs with serialize_overlap enabled.

              Default: false.

       io_submit_mode=str
              This option controls how fio submits the I/O to the  I/O  engine.  The  default  is
              `inline', which means that the fio job threads submit and reap I/O directly. If set
              to `offload', the job threads will offload I/O submission to a  dedicated  pool  of
              I/O  threads. This requires some coordination and thus has a bit of extra overhead,
              especially for lower queue depth I/O where it can increase latencies.  The  benefit
              is  that  fio  can  manage  submission rates independently of the device completion
              rates. This avoids skewed latency reporting if I/O gets backed  up  on  the  device
              side (the coordinated omission problem).

   I/O rate
       thinktime=time
              Stall  the  job  for the specified period of time after an I/O has completed before
              issuing the next. May be used to simulate processing being done by an  application.
              When   the  unit  is  omitted,  the  value  is  interpreted  in  microseconds.  See
              thinktime_blocks and thinktime_spin.

       thinktime_spin=time
              Only valid if thinktime is set - pretend to spend CPU time doing something with the
              data received, before falling back to sleeping for the rest of the period specified
              by thinktime. When the unit is omitted, the value is interpreted in microseconds.

       thinktime_blocks=int
              Only valid if thinktime is set - control how many blocks to issue,  before  waiting
              thinktime usecs. If not set, defaults to 1 which will make fio wait thinktime usecs
              after every block. This effectively makes any queue depth setting redundant,  since
              no  more  than  1  I/O  will  be  queued  before  we have to complete it and do our
              thinktime. In other words, this setting effectively caps the  queue  depth  if  the
              latter is larger.

       rate=int[,int][,int]
              Cap  the  bandwidth used by this job. The number is in bytes/sec, the normal suffix
              rules apply. Comma-separated values may be specified for reads, writes,  and  trims
              as described in blocksize.

              For  example,  using  `rate=1m,500k'  would  limit  reads to 1MiB/sec and writes to
              500KiB/sec. Capping  only  reads  or  writes  can  be  done  with  `rate=,500k'  or
              `rate=500k,' where the former will only limit writes (to 500KiB/sec) and the latter
              will only limit reads.

       rate_min=int[,int][,int]
              Tell fio to do whatever it can to maintain at least this bandwidth. Failing to meet
              this  requirement  will  cause  the  job  to  exit.  Comma-separated  values may be
              specified for reads, writes, and trims as described in blocksize.

       rate_iops=int[,int][,int]
              Cap the bandwidth to this  number  of  IOPS.  Basically  the  same  as  rate,  just
              specified  independently  of  bandwidth.  If  the  job  is given a block size range
              instead of a  fixed  value,  the  smallest  block  size  is  used  as  the  metric.
              Comma-separated  values  may be specified for reads, writes, and trims as described
              in blocksize.

       rate_iops_min=int[,int][,int]
              If  fio  doesn't  meet  this  rate  of  I/O,  it  will  cause  the  job  to   exit.
              Comma-separated  values  may be specified for reads, writes, and trims as described
              in blocksize.

       rate_process=str
              This option controls  how  fio  manages  rated  I/O  submissions.  The  default  is
              `linear', which submits I/O in a linear fashion with fixed delays between I/Os that
              gets adjusted based on I/O completion rates. If this is set to `poisson', fio  will
              submit  I/O  based  on  a more real world random request flow, known as the Poisson
              process (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda  will  be
              10^6 / IOPS for the given workload.

       rate_ignore_thinktime=bool
              By default, fio will attempt to catch up to the specified rate setting, if any kind
              of thinktime setting was used. If this option is set,  then  fio  will  ignore  the
              thinktime and continue doing IO at the specified rate, instead of entering a catch-
              up mode after thinktime is done.

   I/O latency
       latency_target=time
              If set, fio will attempt to find the max performance point that the given  workload
              will  run  at  while  maintaining  a  latency  below  this target. When the unit is
              omitted,  the  value  is  interpreted  in  microseconds.  See  latency_window   and
              latency_percentile.

       latency_window=time
              Used  with  latency_target  to  specify  the  sample  window that the job is run at
              varying queue depths to test the performance. When the unit is omitted,  the  value
              is interpreted in microseconds.

       latency_percentile=float
              The   percentage   of  I/Os  that  must  fall  within  the  criteria  specified  by
              latency_target and latency_window. If not set, this defaults to 100.0, meaning that
              all I/Os must be equal or below to the value set by latency_target.

       max_latency=time
              If  set,  fio  will exit the job with an ETIMEDOUT error if it exceeds this maximum
              latency. When the unit is omitted, the value is interpreted in microseconds.

       rate_cycle=int
              Average bandwidth for rate and rate_min over this number of milliseconds.  Defaults
              to 1000.

   I/O replay
       write_iolog=str
              Write  the  issued  I/O  patterns  to the specified file. See read_iolog. Specify a
              separate file for each job, otherwise the iologs will be interspersed and the  file
              may be corrupt.

       read_iolog=str
              Open  an iolog with the specified filename and replay the I/O patterns it contains.
              This can be used to store a workload and replay it sometime later. The iolog  given
              may  also be a blktrace binary file, which allows fio to replay a workload captured
              by blktrace. See blktrace(8) for how to capture such  logging  data.  For  blktrace
              replay,  the  file  needs  to  be  turned  into  a  blkparse binary data file first
              (`blkparse <device> -o /dev/null -d file_for_fio.bin').  You can specify  a  number
              of files by separating the names with a ':' character.  See the filename option for
              information on how to escape ':' and 'ยด characters within  the  file  names.  These
              files will be sequentially assigned to job clones created by numjobs.

       read_iolog_chunked=bool
              Determines  how iolog is read. If false (default) entire read_iolog will be read at
              once. If selected true, input from iolog will be read gradually.  Useful when iolog
              is very large, or it is generated.

       merge_blktrace_file=str
              When  specified,  rather  than replaying the logs passed to read_iolog, the logs go
              through a merge phase which aggregates them into a single blktrace.  The  resulting
              file  is  then passed on as the read_iolog parameter. The intention here is to make
              the order of events consistent. This limits the influence of the scheduler compared
              to replaying multiple blktraces via concurrent jobs.

       merge_blktrace_scalars=float_list
              This  is  a  percentage  based  option  that is index paired with the list of files
              passed to read_iolog. When merging is performed, scale the time of  each  event  by
              the corresponding amount. For example, `--merge_blktrace_scalars="50:100"' runs the
              first trace in halftime and the second trace in realtime. This knob  is  separately
              tunable  from  replay_time_scale which scales the trace during runtime and will not
              change the output of the merge unlike this option.

       merge_blktrace_iters=float_list
              This is a whole number option that is index paired with the list of files passed to
              read_iolog.  When  merging is performed, run each trace for the specified number of
              iterations. For example, `--merge_blktrace_iters="2:1"' runs the  first  trace  for
              two iterations and the second trace for one iteration.

       replay_no_stall=bool
              When  replaying  I/O  with read_iolog the default behavior is to attempt to respect
              the timestamps within the log and replay them with the  appropriate  delay  between
              IOPS.  By  setting this variable fio will not respect the timestamps and attempt to
              replay them as fast as possible while still respecting ordering. The result is  the
              same I/O pattern to a given device, but different timings.

       replay_time_scale=int
              When  replaying  I/O  with  read_iolog,  fio  will honor the original timing in the
              trace. With this option, it's possible to scale the time. It's a percentage option,
              if  set to 50 it means run at 50% the original IO rate in the trace. If set to 200,
              run at twice the original IO rate. Defaults to 100.

       replay_redirect=str
              While replaying I/O patterns using read_iolog the default behavior is to replay the
              IOPS onto the major/minor device that each IOP was recorded from. This is sometimes
              undesirable because on a different machine those major/minor numbers can map  to  a
              different  device.  Changing  hardware  on  the  same  system  can also result in a
              different major/minor mapping.  replay_redirect causes all I/Os to be replayed onto
              the  single  specified  device  regardless of the device it was recorded from. i.e.
              `replay_redirect=/dev/sdc' would cause all I/O in  the  blktrace  or  iolog  to  be
              replayed  onto  `/dev/sdc'.  This  means  multiple  devices will be replayed onto a
              single device, if the trace contains multiple devices. If you want multiple devices
              to  be  replayed concurrently to multiple redirected devices you must blkparse your
              trace into separate traces  and  replay  them  with  independent  fio  invocations.
              Unfortunately  this  also  breaks  the strict time ordering between multiple device
              accesses.

       replay_align=int
              Force alignment of the byte offsets in a trace to this value. The value must  be  a
              power of 2.

       replay_scale=int
              Scale bye offsets down by this factor when replaying traces. Should most likely use
              replay_align as well.

   Threads, processes and job synchronization
       replay_skip=str
              Sometimes it's useful to skip certain IO types in a replay trace.  This  could  be,
              for   instance,  eliminating  the  writes  in  the  trace.  Or  not  replaying  the
              trims/discards, if you are redirecting to a device that doesn't support them.  This
              option takes a comma separated list of read, write, trim, sync.

       thread Fio  defaults  to creating jobs by using fork, however if this option is given, fio
              will create jobs by using  POSIX  Threads'  function  pthread_create(3)  to  create
              threads instead.

       wait_for=str
              If  set, the current job won't be started until all workers of the specified waitee
              job are done.  wait_for operates on  the  job  name  basis,  so  there  are  a  few
              limitations.  First, the waitee must be defined prior to the waiter job (meaning no
              forward references). Second, if a job is being referenced as a waitee, it must have
              a unique name (no duplicate waitees).

       nice=int
              Run  the  job  with the given nice value. See man nice(2).  On Windows, values less
              than -15 set the process class to "High"; -1 through  -15  set  "Above  Normal";  1
              through 15 "Below Normal"; and above 15 "Idle" priority class.

       prio=int
              Set the I/O priority value of this job. Linux limits us to a positive value between
              0 and 7, with 0 being the highest. See  man  ionice(1).  Refer  to  an  appropriate
              manpage for other operating systems since meaning of priority may differ.

       prioclass=int
              Set the I/O priority class. See man ionice(1).

       cpus_allowed=str
              Controls  the  same  options as cpumask, but accepts a textual specification of the
              permitted CPUs instead and CPUs are indexed from 0. So to use  CPUs  0  and  5  you
              would  specify  `cpus_allowed=0,5'.  This  option also allows a range of CPUs to be
              specified -- say you wanted a binding to CPUs 0, 5, and 8  to  15,  you  would  set
              `cpus_allowed=0,5,8-15'.

              On  Windows,  when  `cpus_allowed'  is unset only CPUs from fio's current processor
              group will be used and affinity settings are inherited  from  the  system.  An  fio
              build  configured  to  target Windows 7 makes options that set CPUs processor group
              aware and values will set both the processor group  and  a  CPU  from  within  that
              group.  For  example, on a system where processor group 0 has 40 CPUs and processor
              group 1 has 32 CPUs, `cpus_allowed' values between 0 and 39  will  bind  CPUs  from
              processor  group  0 and `cpus_allowed' values between 40 and 71 will bind CPUs from
              processor group 1. When using `cpus_allowed_policy=shared' all CPUs specified by  a
              single `cpus_allowed' option must be from the same processor group. For Windows fio
              builds not built for Windows 7, CPUs will only be selected from  (and  be  relative
              to)  whatever  processor  group  fio  happens  to be running in and CPUs from other
              processor groups cannot be used.

       cpus_allowed_policy=str
              Set the policy of how  fio  distributes  the  CPUs  specified  by  cpus_allowed  or
              cpumask. Two policies are supported:

                     shared All jobs will share the CPU set specified.

                     split  Each job will get a unique CPU from the CPU set.

              shared  is  the  default  behavior,  if  the  option  isn't  specified. If split is
              specified, then fio will will assign one cpu per job. If not enough CPUs are  given
              for the jobs listed, then fio will roundrobin the CPUs in the set.

       cpumask=int
              Set the CPU affinity of this job. The parameter given is a bit mask of allowed CPUs
              the job may run on. So if you want the allowed CPUs to be 1 and 5, you  would  pass
              the  decimal  value of (1 << 1 | 1 << 5), or 34. See man sched_setaffinity(2). This
              may not work on all supported operating systems or  kernel  versions.  This  option
              doesn't  work  well  for  a  higher CPU count than what you can store in an integer
              mask, so it can only control cpus 1-32. For  boxes  with  larger  CPU  counts,  use
              cpus_allowed.

       numa_cpu_nodes=str
              Set  this  job  running  on  specified  NUMA nodes' CPUs. The arguments allow comma
              delimited list of cpu numbers, A-B ranges, or `all'. Note, to enable  NUMA  options
              support, fio must be built on a system with libnuma-dev(el) installed.

       numa_mem_policy=str
              Set this job's memory policy and corresponding NUMA nodes. Format of the arguments:

                     <mode>[:<nodelist>]

              `mode'  is  one  of  the  following  memory  policies: `default', `prefer', `bind',
              `interleave' or `local'. For `default' and `local' memory policies, no  node  needs
              to  be  specified.  For  `prefer',  only  one  node  is  allowed.  For  `bind'  and
              `interleave' the `nodelist' may be as follows: a comma delimited list  of  numbers,
              A-B ranges, or `all'.

       cgroup=str
              Add  job to this control group. If it doesn't exist, it will be created. The system
              must have a mounted cgroup blkio mount point for  this  to  work.  If  your  system
              doesn't have it mounted, you can do so with:

                     # mount -t cgroup -o blkio none /cgroup

       cgroup_weight=int
              Set  the  weight of the cgroup to this value. See the documentation that comes with
              the kernel, allowed values are in the range of 100..1000.

       cgroup_nodelete=bool
              Normally fio will delete the cgroups it has created after the  job  completion.  To
              override  this  behavior  and to leave cgroups around after the job completion, set
              `cgroup_nodelete=1'. This can be useful if one  wants  to  inspect  various  cgroup
              files after job completion. Default: false.

       flow_id=int
              The ID of the flow. If not specified, it defaults to being a global flow. See flow.

       flow=int
              Weight  in  token-based  flow control. If this value is used, then there is a 'flow
              counter' which is used to regulate the proportion of activity between two  or  more
              jobs.  Fio  attempts to keep this flow counter near zero. The flow parameter stands
              for how much should be added or subtracted to the flow counter on each iteration of
              the  main I/O loop. That is, if one job has `flow=8' and another job has `flow=-1',
              then there will be a roughly 1:8 ratio in how much one runs vs the other.

       flow_watermark=int
              The maximum value that the absolute value of the flow counter is allowed  to  reach
              before the job must wait for a lower value of the counter.

       flow_sleep=int
              The  period  of  time,  in  microseconds, to wait after the flow watermark has been
              exceeded before retrying operations.

       stonewall, wait_for_previous
              Wait for preceding jobs in the job file to exit, before starting this one.  Can  be
              used  to  insert  serialization  points  in the job file. A stone wall also implies
              starting a new reporting group, see group_reporting.

       exitall
              By default, fio will continue running all other jobs  when  one  job  finishes  but
              sometimes  this  is  not  the desired action. Setting exitall will instead make fio
              terminate all other jobs when one job finishes.

       exec_prerun=str
              Before running this job, issue the command specified through system(3).  Output  is
              redirected in a file called `jobname.prerun.txt'.

       exec_postrun=str
              After  the  job  completes, issue the command specified though system(3). Output is
              redirected in a file called `jobname.postrun.txt'.

       uid=int
              Instead of running as the invoking user, set the user ID to this value  before  the
              thread/process does any work.

       gid=int
              Set group ID, see uid.

   Verification
       verify_only
              Do  not  perform  specified  workload,  only  verify  data  still  matches previous
              invocation of this workload. This option allows one to check data multiple times at
              a  later  date  without  overwriting it. This option makes sense only for workloads
              that write data, and does not support workloads with the time_based option set.

       do_verify=bool
              Run the verify phase after a write phase. Only valid if  verify  is  set.  Default:
              true.

       verify=str
              If  writing to a file, fio can verify the file contents after each iteration of the
              job. Each verification method also implies verification of special header, which is
              written to the beginning of each block. This header also includes meta information,
              like offset of the block, block number, timestamp  when  block  was  written,  etc.
              verify can be combined with verify_pattern option. The allowed values are:

                     md5    Use  an  md5  sum of the data area and store it in the header of each
                            block.

                     crc64  Use an experimental crc64 sum of the data area and store  it  in  the
                            header of each block.

                     crc32c Use  a crc32c sum of the data area and store it in the header of each
                            block. This will automatically use hardware acceleration (e.g. SSE4.2
                            on  an  x86  or CRC crypto extensions on ARM64) but will fall back to
                            software crc32c if none is found. Generally the fastest checksum  fio
                            supports when hardware accelerated.

                     crc32c-intel
                            Synonym for crc32c.

                     crc32  Use  a  crc32 sum of the data area and store it in the header of each
                            block.

                     crc16  Use a crc16 sum of the data area and store it in the header  of  each
                            block.

                     crc7   Use  a  crc7  sum of the data area and store it in the header of each
                            block.

                     xxhash Use xxhash as the checksum function. Generally the  fastest  software
                            checksum that fio supports.

                     sha512 Use sha512 as the checksum function.

                     sha256 Use sha256 as the checksum function.

                     sha1   Use optimized sha1 as the checksum function.

                     sha3-224
                            Use optimized sha3-224 as the checksum function.

                     sha3-256
                            Use optimized sha3-256 as the checksum function.

                     sha3-384
                            Use optimized sha3-384 as the checksum function.

                     sha3-512
                            Use optimized sha3-512 as the checksum function.

                     meta   This  option is deprecated, since now meta information is included in
                            generic verification header and meta verification happens by default.
                            For  detailed  information see the description of the verify setting.
                            This  option  is  kept  because  of  compatibility's  sake  with  old
                            configurations. Do not use it.

                     pattern
                            Verify  a  strict  pattern.  Normally fio includes a header with some
                            basic information and checksumming, but if this option is  set,  only
                            the specific pattern set with verify_pattern is verified.

                     null   Only   pretend   to   verify.   Useful  for  testing  internals  with
                            `ioengine=null', not for much else.

              This option can be used for repeated burn-in tests of a system to  make  sure  that
              the written data is also correctly read back. If the data direction given is a read
              or random read, fio will assume that it should verify a previously written file. If
              the  data  direction  includes  any  form of write, the verify will be of the newly
              written data.

              To avoid false  verification  errors,  do  not  use  the  norandommap  option  when
              verifying  data  with async I/O engines and I/O depths > 1.  Or use the norandommap
              and the lfsr random generator together to avoid writing to  the  same  offset  with
              muliple outstanding I/Os.

       verify_offset=int
              Swap  the verification header with data somewhere else in the block before writing.
              It is swapped back before verifying.

       verify_interval=int
              Write the verification header at a finer granularity than the blocksize. It will be
              written  for  chunks  the  size  of  verify_interval.  blocksize should divide this
              evenly.

       verify_pattern=str
              If set, fio will fill the I/O buffers with this pattern. Fio  defaults  to  filling
              with  totally  random  bytes,  but  sometimes it's interesting to fill with a known
              pattern for I/O verification purposes. Depending on the width of the  pattern,  fio
              will  fill 1/2/3/4 bytes of the buffer at the time (it can be either a decimal or a
              hex number). The verify_pattern if larger than a 32-bit quantity has to  be  a  hex
              number  that starts with either "0x" or "0X". Use with verify. Also, verify_pattern
              supports %o format, which means that for each block offset will be written and then
              verified back, e.g.:

                     verify_pattern=%o

              Or use combination of everything:

                     verify_pattern=0xff%o"abcd"-12

       verify_fatal=bool
              Normally  fio  will  keep  checking  the entire contents before quitting on a block
              verification failure. If this option is set, fio will exit the  job  on  the  first
              observed failure. Default: false.

       verify_dump=bool
              If  set,  dump  the  contents of both the original data block and the data block we
              read off disk to files. This allows later analysis to inspect  just  what  kind  of
              data corruption occurred. Off by default.

       verify_async=int
              Fio  will  normally verify I/O inline from the submitting thread. This option takes
              an integer describing how many async offload threads to create for I/O verification
              instead,  causing  fio to offload the duty of verifying I/O contents to one or more
              separate threads. If using this offload option, even sync I/O engines  can  benefit
              from  using  an  iodepth  setting  higher  than 1, as it allows them to have I/O in
              flight while verifies are running.  Defaults to 0 async threads, i.e.  verification
              is not asynchronous.

       verify_async_cpus=str
              Tell  fio  to set the given CPU affinity on the async I/O verification threads. See
              cpus_allowed for the format used.

       verify_backlog=int
              Fio will normally verify the written contents of a job that  utilizes  verify  once
              that  job  has  completed. In other words, everything is written then everything is
              read back and verified. You may want to verify continually instead for a variety of
              reasons.  Fio  stores  the meta data associated with an I/O block in memory, so for
              large verify workloads, quite a bit of memory would be used up  holding  this  meta
              data.  If  this  option  is  enabled, fio will write only N blocks before verifying
              these blocks.

       verify_backlog_batch=int
              Control how many blocks fio will verify if verify_backlog is set. If not set,  will
              default  to  the value of verify_backlog (meaning the entire queue is read back and
              verified). If verify_backlog_batch is less than verify_backlog then not all  blocks
              will  be  verified,  if  verify_backlog_batch  is  larger than verify_backlog, some
              blocks will be verified more than once.

       verify_state_save=bool
              When a job exits during the write phase of a  verify  workload,  save  its  current
              state. This allows fio to replay up until that point, if the verify state is loaded
              for the verify read phase. The format of the filename is, roughly:

                     <type>-<jobname>-<jobindex>-verify.state.

              <type> is "local" for a local run, "sock" for a  client/server  socket  connection,
              and  "ip"  (192.168.0.1,  for  instance)  for a networked client/server connection.
              Defaults to true.

       verify_state_load=bool
              If a verify termination trigger was used, fio stores the  current  write  state  of
              each  thread.  This  can  be used at verification time so that fio knows how far it
              should verify. Without this information, fio will run  a  full  verification  pass,
              according to the settings in the job file used. Default false.

       trim_percentage=int
              Number of verify blocks to discard/trim.

       trim_verify_zero=bool
              Verify that trim/discarded blocks are returned as zeros.

       trim_backlog=int
              Verify that trim/discarded blocks are returned as zeros.

       trim_backlog_batch=int
              Trim this number of I/O blocks.

       experimental_verify=bool
              Enable experimental verification.

   Steady state
       steadystate=str:float, ss=str:float
              Define  the  criterion  and limit for assessing steady state performance. The first
              parameter designates the criterion whereas the second parameter sets the threshold.
              When  the  criterion  falls below the threshold for the specified duration, the job
              will stop. For example, `iops_slope:0.1%' will direct fio to terminate the job when
              the  least  squares  regression  slope  falls  below  0.1%  of  the  mean  IOPS. If
              group_reporting is enabled this will apply to all jobs in the group. Below  is  the
              list of available steady state assessment criteria. All assessments are carried out
              using only data from  the  rolling  collection  window.  Threshold  limits  can  be
              expressed as a fixed value or as a percentage of the mean in the collection window.

              When  using  this  feature,  most  jobs  should  include the time_based and runtime
              options or the loops option so that fio does not stop running after it has  covered
              the full size of the specified file(s) or device(s).

                            iops   Collect  IOPS  data.  Stop  the  job  if  all  individual IOPS
                                   measurements are within the specified limit of the  mean  IOPS
                                   (e.g.,  `iops:2' means that all individual IOPS values must be
                                   within 2 of the  mean,  whereas  `iops:0.2%'  means  that  all
                                   individual IOPS values must be within 0.2% of the mean IOPS to
                                   terminate the job).

                            iops_slope
                                   Collect IOPS data and calculate the least  squares  regression
                                   slope.  Stop  the  job  if the slope falls below the specified
                                   limit.

                            bw     Collect  bandwidth  data.  Stop  the  job  if  all  individual
                                   bandwidth  measurements  are within the specified limit of the
                                   mean bandwidth.

                            bw_slope
                                   Collect  bandwidth  data  and  calculate  the  least   squares
                                   regression  slope.  Stop  the job if the slope falls below the
                                   specified limit.

              steadystate_duration=time, ss_dur=time
                     A rolling window of this duration will be used to judge whether steady state
                     has  been  reached. Data will be collected once per second. The default is 0
                     which disables steady state detection. When the unit is omitted,  the  value
                     is interpreted in seconds.

              steadystate_ramp_time=time, ss_ramp=time
                     Allow  the  job  to  run  for  the  specified duration before beginning data
                     collection for checking the steady  state  job  termination  criterion.  The
                     default is 0. When the unit is omitted, the value is interpreted in seconds.

   Measurements and reporting
       per_job_logs=bool
              If  set,  this  generates  bw/clat/iops log with per file private filenames. If not
              set, jobs with identical names will share the log filename. Default: true.

       group_reporting
              It may sometimes be interesting to display statistics for groups of jobs as a whole
              instead  of  for  each  individual job. This is especially true if numjobs is used;
              looking at individual thread/process output quickly becomes unwieldy.  To  see  the
              final report per-group instead of per-job, use group_reporting. Jobs in a file will
              be part of the same reporting group, unless if separated  by  a  stonewall,  or  by
              using new_group.

       new_group
              Start a new reporting group. See: group_reporting. If not given, all jobs in a file
              will be part of the same reporting group, unless separated by a stonewall.

       stats=bool
              By default, fio collects and shows final output results for all jobs that  run.  If
              this option is set to 0, then fio will ignore it in the final stat output.

       write_bw_log=str
              If  given,  write  a  bandwidth  log for this job. Can be used to store data of the
              bandwidth of the jobs in their lifetime.

              If no str argument is given, the default filename of `jobname_type.x.log' is  used.
              Even  when  the argument is given, fio will still append the type of log. So if one
              specifies:

                     write_bw_log=foo

              The actual log name will be `foo_bw.x.log' where `x' is the index of the job (1..N,
              where  N  is  the number of jobs). If per_job_logs is false, then the filename will
              not include the `.x` job index.

              The included fio_generate_plots script uses gnuplot to turn these text  files  into
              nice graphs. See the LOG FILE FORMATS section for how data is structured within the
              file.

       write_lat_log=str
              Same  as  write_bw_log,  except  this  option   creates   I/O   submission   (e.g.,
              `name_slat.x.log'),   completion   (e.g.,   `name_clat.x.log'),  and  total  (e.g.,
              `name_lat.x.log') latency files instead. See write_bw_log  for  details  about  the
              filename  format and the LOG FILE FORMATS section for how data is structured within
              the files.

       write_hist_log=str
              Same as write_bw_log but writes an I/O completion  latency  histogram  file  (e.g.,
              `name_hist.x.log')  instead. Note that this file will be empty unless log_hist_msec
              has also been set.  See write_bw_log for details about the filename format and  the
              LOG FILE FORMATS section for how data is structured within the file.

       write_iops_log=str
              Same  as  write_bw_log,  but writes an IOPS file (e.g.  `name_iops.x.log`) instead.
              Because fio defaults to individual I/O logging, the value entry  in  the  IOPS  log
              will  be  1  unless  windowed  logging  (see  log_avg_msec)  has  been enabled. See
              write_bw_log for details about the filename format and LOG  FILE  FORMATS  for  how
              data is structured within the file.

       log_avg_msec=int
              By  default,  fio  will  log an entry in the iops, latency, or bw log for every I/O
              that completes. When writing to the disk log, that can quickly grow to a very large
              size.  Setting  this option makes fio average the each log entry over the specified
              period of time, reducing the resolution of the  log.  See  log_max_value  as  well.
              Defaults to 0, logging all entries.  Also see LOG FILE FORMATS section.

       log_hist_msec=int
              Same as log_avg_msec, but logs entries for completion latency histograms. Computing
              latency percentiles from averages of intervals using  log_avg_msec  is  inaccurate.
              Setting  this  option  makes fio log histogram entries over the specified period of
              time, reducing log sizes for high IOPS devices while retaining percentile accuracy.
              See  log_hist_coarseness  and  write_hist_log  as  well.   Defaults  to  0, meaning
              histogram logging is disabled.

       log_hist_coarseness=int
              Integer ranging from 0 to 6, defining the  coarseness  of  the  resolution  of  the
              histogram  logs  enabled  with log_hist_msec. For each increment in coarseness, fio
              outputs half as many bins. Defaults to 0, for which  histogram  logs  contain  1216
              latency bins. See LOG FILE FORMATS section.

       log_max_value=bool
              If  log_avg_msec is set, fio logs the average over that window. If you instead want
              to log the maximum value, set this  option  to  1.  Defaults  to  0,  meaning  that
              averaged values are logged.

       log_offset=bool
              If this is set, the iolog options will include the byte offset for the I/O entry as
              well as the other data values. Defaults to 0 meaning that offsets are  not  present
              in logs. Also see LOG FILE FORMATS section.

       log_compression=int
              If  this  is  set,  fio  will  compress the I/O logs as it goes, to keep the memory
              footprint lower. When a log reaches the specified size, that chunk is  removed  and
              compressed  in  the background. Given that I/O logs are fairly highly compressible,
              this yields a nice memory savings  for  longer  runs.  The  downside  is  that  the
              compression  will  consume  some  background  CPU cycles, so it may impact the run.
              This, however, is also true if the logging ends up consuming  most  of  the  system
              memory.  So  pick your poison. The I/O logs are saved normally at the end of a run,
              by decompressing the chunks and storing  them  in  the  specified  log  file.  This
              feature depends on the availability of zlib.

       log_compression_cpus=str
              Define  the  set  of CPUs that are allowed to handle online log compression for the
              I/O jobs. This can provide better isolation between performance sensitive jobs, and
              background compression work. See cpus_allowed for the format used.

       log_store_compressed=bool
              If  set,  fio  will  store  the  log  files  in  a  compressed  format. They can be
              decompressed with fio, using the --inflate-log command line  parameter.  The  files
              will be stored with a `.fz' suffix.

       log_unix_epoch=bool
              If  set,  fio  will  log  Unix  timestamps  to  the  log files produced by enabling
              write_type_log for each log type, instead of the default zero-based timestamps.

       block_error_percentiles=bool
              If set, record errors in trim block-sized units from writes and trims and output  a
              histogram  of  how  many trims it took to get to errors, and what kind of error was
              encountered.

       bwavgtime=int
              Average the calculated bandwidth  over  the  given  time.  Value  is  specified  in
              milliseconds. If the job also does bandwidth logging through write_bw_log, then the
              minimum of this option and log_avg_msec will be used. Default: 500ms.

       iopsavgtime=int
              Average  the  calculated  IOPS  over  the  given  time.  Value  is   specified   in
              milliseconds.  If  the  job also does IOPS logging through write_iops_log, then the
              minimum of this option and log_avg_msec will be used. Default: 500ms.

       disk_util=bool
              Generate disk utilization statistics, if the platform supports it.  Default: true.

       disable_lat=bool
              Disable measurements of total latency numbers. Useful only  for  cutting  back  the
              number  of calls to gettimeofday(2), as that does impact performance at really high
              IOPS rates. Note that to really get rid of a large  amount  of  these  calls,  this
              option must be used with disable_slat and disable_bw_measurement as well.

       disable_clat=bool
              Disable measurements of completion latency numbers. See disable_lat.

       disable_slat=bool
              Disable measurements of submission latency numbers. See disable_lat.

       disable_bw_measurement=bool, disable_bw=bool
              Disable measurements of throughput/bandwidth numbers. See disable_lat.

       clat_percentiles=bool
              Enable  the  reporting  of  percentiles  of  completion  latencies.  This option is
              mutually exclusive with lat_percentiles.

       lat_percentiles=bool
              Enable  the  reporting  of  percentiles  of  I/O  latencies.  This  is  similar  to
              clat_percentiles, except that this includes the submission latency.  This option is
              mutually exclusive with clat_percentiles.

       percentile_list=float_list
              Overwrite the default list of percentiles for completion latencies  and  the  block
              error  histogram.  Each  number  is a floating number in the range (0,100], and the
              maximum length of the list is 20. Use ':' to separate the  numbers,  and  list  the
              numbers  in  ascending order. For example, `--percentile_list=99.5:99.9' will cause
              fio to report the values of completion latency below which 99.5% and 99.9%  of  the
              observed latencies fell, respectively.

       significant_figures=int
              If  using  --output-format  of `normal', set the significant figures to this value.
              Higher values will yield more precise IOPS and throughput units, while lower values
              will round. Requires a minimum value of 1 and a maximum value of 10. Defaults to 4.

   Error handling
       exitall_on_error
              When one job finishes in error, terminate the rest. The default is to wait for each
              job to finish.

       continue_on_error=str
              Normally fio will exit the job on the first observed failure.  If  this  option  is
              set,  fio  will  continue the job when there is a 'non-fatal error' (EIO or EILSEQ)
              until the runtime is exceeded or the I/O  size  specified  is  completed.  If  this
              option  is  used, there are two more stats that are appended, the total error count
              and the first error. The error field given in the stats is the first error that was
              hit during the run.  The allowed values are:

                     none   Exit on any I/O or verify errors.

                     read   Continue on read errors, exit on all others.

                     write  Continue on write errors, exit on all others.

                     io     Continue on any I/O error, exit on all others.

                     verify Continue on verify errors, exit on all others.

                     all    Continue on all errors.

                     0      Backward-compatible alias for 'none'.

                     1      Backward-compatible alias for 'all'.

       ignore_error=str
              Sometimes  you  want to ignore some errors during test in that case you can specify
              error list for each error type, instead of only being able to  ignore  the  default
              'non-fatal               error'               using              continue_on_error.
              `ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST' errors for given  error
              type  is  separated  with ':'. Error may be symbol ('ENOSPC', 'ENOMEM') or integer.
              Example:

                     ignore_error=EAGAIN,ENOSPC:122

              This option will ignore EAGAIN from READ, and ENOSPC and  122(EDQUOT)  from  WRITE.
              This  option works by overriding continue_on_error with the list of errors for each
              error type if any.

       error_dump=bool
              If set dump every error even if it is non fatal, true by default. If disabled  only
              fatal error will be dumped.

   Running predefined workloads
       Fio includes predefined profiles that mimic the I/O workloads generated by other tools.

       profile=str
              The predefined workload to run. Current profiles are:

                     tiobench
                            Threaded I/O bench (tiotest/tiobench) like workload.

                     act    Aerospike Certification Tool (ACT) like workload.

       To  view  a  profile's  additional options use --cmdhelp after specifying the profile. For
       example:

              $ fio --profile=act --cmdhelp

   Act profile options
       device-names=str
              Devices to use.

       load=int
              ACT load multiplier. Default: 1.

       test-duration=time
              How long the entire test takes to run. When the unit is omitted, the value is given
              in seconds. Default: 24h.

       threads-per-queue=int
              Number of read I/O threads per device. Default: 8.

       read-req-num-512-blocks=int
              Number of 512B blocks to read at the time. Default: 3.

       large-block-op-kbytes=int
              Size of large block ops in KiB (writes). Default: 131072.

       prep   Set to run ACT prep phase.

   Tiobench profile options
       size=str
              Size in MiB.

       block=int
              Block size in bytes. Default: 4096.

       numruns=int
              Number of runs.

       dir=str
              Test directory.

       threads=int
              Number of threads.

OUTPUT

       Fio  spits  out  a  lot  of output. While running, fio will display the status of the jobs
       created. An example of that would be:

                 Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]

       The characters inside the first set of square brackets denote the current status  of  each
       thread.  The  first  character is the first job defined in the job file, and so forth. The
       possible values (in typical life cycle order) are:

              P      Thread setup, but not started.
              C      Thread created.
              I      Thread initialized, waiting or generating necessary data.
              p      Thread running pre-reading file(s).
              /      Thread is in ramp period.
              R      Running, doing sequential reads.
              r      Running, doing random reads.
              W      Running, doing sequential writes.
              w      Running, doing random writes.
              M      Running, doing mixed sequential reads/writes.
              m      Running, doing mixed random reads/writes.
              D      Running, doing sequential trims.
              d      Running, doing random trims.
              F      Running, currently waiting for fsync(2).
              V      Running, doing verification of written data.
              f      Thread finishing.
              E      Thread exited, not reaped by main thread yet.
              -      Thread reaped.
              X      Thread reaped, exited with an error.
              K      Thread reaped, exited due to signal.

       Fio will condense the thread string as not to take up more space on the command line  than
       needed. For instance, if you have 10 readers and 10 writers running, the output would look
       like this:

                 Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]

       Note that the status string is displayed in order, so it's possible to tell which  of  the
       jobs are currently doing what. In the example above this means that jobs 1--10 are readers
       and 11--20 are writers.

       The other values are fairly self explanatory -- number of threads  currently  running  and
       doing  I/O,  the number of currently open files (f=), the estimated completion percentage,
       the rate of I/O since last check (read speed listed first, then write speed and optionally
       trim speed) in terms of bandwidth and IOPS, and time to completion for the current running
       group. It's impossible to estimate runtime of the following groups (if any).

       When fio is done (or interrupted by Ctrl-C), it will show the data for each thread,  group
       of  threads,  and disks in that order. For each overall thread (or group) the output looks
       like:

                 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
                   write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
                     slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
                     clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
                      lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
                     clat percentiles (usec):
                      |  1.00th=[  302],  5.00th=[  326], 10.00th=[  343], 20.00th=[  363],
                      | 30.00th=[  392], 40.00th=[  404], 50.00th=[  416], 60.00th=[  445],
                      | 70.00th=[  816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
                      | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
                      | 99.99th=[78119]
                    bw (  KiB/s): min=  532, max=  686, per=0.10%, avg=622.87, stdev=24.82, samples=  100
                    iops        : min=   76, max=   98, avg=88.98, stdev= 3.54, samples=  100
                   lat (usec)   : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
                   lat (msec)   : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
                   lat (msec)   : 100=0.65%
                   cpu          : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
                   IO depths    : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
                      submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
                      complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
                      issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
                      latency   : target=0, window=0, percentile=100.00%, depth=8

       The job name (or first job's name when using group_reporting) is printed, along  with  the
       group id, count of jobs being aggregated, last error id seen (which is 0 when there are no
       errors), pid/tid of that thread and the time the job/group completed. Below  are  the  I/O
       statistics for each data direction performed (showing writes in the example above). In the
       order listed, they denote:

              read/write/trim
                     The string before the colon shows the I/O direction the statistics are  for.
                     IOPS  is  the average I/Os performed per second. BW is the average bandwidth
                     rate shown as: value in power of 2 format (value in power of 10 format). The
                     last two values show: (total I/O performed in power of 2 format / runtime of
                     that thread).

              slat   Submission latency (min being the minimum, max being the maximum, avg  being
                     the  average,  stdev being the standard deviation). This is the time it took
                     to submit the I/O. For sync I/O this row is not displayed  as  the  slat  is
                     really the completion latency (since queue/complete is one operation there).
                     This value can be in nanoseconds, microseconds or milliseconds --- fio  will
                     choose  the  most  appropriate  base  and  print  that (in the example above
                     nanoseconds was the best scale).  Note:  in  --minimal  mode  latencies  are
                     always expressed in microseconds.

              clat   Completion  latency.  Same  names  as  slat,  this  denotes  the  time  from
                     submission to completion of the I/O pieces. For sync I/O, clat will  usually
                     be  equal  (or  very  close)  to  0,  as the time from submit to complete is
                     basically just CPU time (I/O has already been done, see slat explanation).

              lat    Total latency. Same names as slat and clat, this denotes the time from  when
                     fio created the I/O unit to completion of the I/O operation.

              bw     Bandwidth  statistics  based  on  samples. Same names as the xlat stats, but
                     also includes the number of  samples  taken  (samples)  and  an  approximate
                     percentage  of  total  aggregate bandwidth this thread received in its group
                     (per). This last value is only really useful if the threads  in  this  group
                     are on the same disk, since they are then competing for disk access.

              iops   IOPS statistics based on samples. Same names as bw.

              lat (nsec/usec/msec)
                     The distribution of I/O completion latencies. This is the time from when I/O
                     leaves fio and when it gets completed. Unlike the  separate  read/write/trim
                     sections  above,  the  data  here and in the remaining sections apply to all
                     I/Os for the reporting  group.  250=0.04%  means  that  0.04%  of  the  I/Os
                     completed  in under 250us. 500=64.11% means that 64.11% of the I/Os required
                     250 to 499us for completion.

              cpu    CPU usage. User and system time, along with the number of  context  switches
                     this  thread  went  through,  usage of system and user time, and finally the
                     number of major and minor page  faults.  The  CPU  utilization  numbers  are
                     averages  for  the jobs in that reporting group, while the context and fault
                     counters are summed.

              IO depths
                     The distribution of I/O depths  over  the  job  lifetime.  The  numbers  are
                     divided  into powers of 2 and each entry covers depths from that value up to
                     those that are lower than the next entry -- e.g., 16= covers depths from  16
                     to  31.  Note  that  the  range covered by a depth distribution entry can be
                     different  to  the  range  covered   by   the   equivalent   submit/complete
                     distribution entry.

              IO submit
                     How  many  pieces of I/O were submitting in a single submit call. Each entry
                     denotes that amount and below, until the previous  entry  --  e.g.,  16=100%
                     means  that we submitted anywhere between 9 to 16 I/Os per submit call. Note
                     that the range covered by a submit distribution entry can  be  different  to
                     the range covered by the equivalent depth distribution entry.

              IO complete
                     Like the above submit number, but for completions instead.

              IO issued rwt
                     The  number  of  read/write/trim  requests issued, and how many of them were
                     short or dropped.

              IO latency
                     These values are for latency_target and related options. When these  options
                     are  engaged,  this  section  describes  the  I/O depth required to meet the
                     specified latency target.

       After each client has been listed, the group statistics are printed. They will  look  like
       this:

                 Run status group 0 (all jobs):
                    READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
                   WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec

       For each data direction it prints:

              bw     Aggregate  bandwidth  of  threads  in this group followed by the minimum and
                     maximum bandwidth of all the threads  in  this  group.   Values  outside  of
                     brackets  are power-of-2 format and those within are the equivalent value in
                     a power-of-10 format.

              io     Aggregate I/O performed of all threads in this group. The format is the same
                     as bw.

              run    The smallest and longest runtimes of the threads in this group.

       And finally, the disk statistics are printed. This is Linux specific.  They will look like
       this:

                   Disk stats (read/write):
                     sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%

       Each value is printed for both reads and writes, with reads first. The numbers denote:

              ios    Number of I/Os performed by all groups.

              merge  Number of merges performed by the I/O scheduler.

              ticks  Number of ticks we kept the disk busy.

              in_queue
                     Total time spent in the disk queue.

              util   The disk  utilization.  A  value  of  100%  means  we  kept  the  disk  busy
                     constantly, 50% would be a disk idling half of the time.

       It  is  also  possible  to get fio to dump the current output while it is running, without
       terminating the job. To do that, send fio the USR1 signal.  You  can  also  get  regularly
       timed  dumps  by  using  the  --status-interval parameter, or by creating a file in `/tmp'
       named `fio-dump-status'. If fio sees this file, it will unlink it  and  dump  the  current
       output status.

TERSE OUTPUT

       For  scripted  usage where you typically want to generate tables or graphs of the results,
       fio can output the results in a semicolon separated format. The format is one long line of
       values, such as:

                 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
                 A description of this job goes here.

       The job description (if provided) follows on a second line.

       To enable terse output, use the --minimal or `--output-format=terse' command line options.
       The first value is the version of the terse output format. If the output has to be changed
       for some reason, this number will be incremented by 1 to signify that change.

       Split  up,  the  format  is  as  follows  (comments  in  brackets  denote when a field was
       introduced or whether it's specific to some terse version):

                      terse version, fio version [v3], jobname, groupid, error

              READ status:

                      Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
                      Submission latency: min, max, mean, stdev (usec)
                      Completion latency: min, max, mean, stdev (usec)
                      Completion latency percentiles: 20 fields (see below)
                      Total latency: min, max, mean, stdev (usec)
                      Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
                      IOPS [v5]: min, max, mean, stdev, number of samples

              WRITE status:

                      Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
                      Submission latency: min, max, mean, stdev (usec)
                      Completion latency: min, max, mean, stdev (usec)
                      Completion latency percentiles: 20 fields (see below)
                      Total latency: min, max, mean, stdev (usec)
                      Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
                      IOPS [v5]: min, max, mean, stdev, number of samples

              TRIM status [all but version 3]:

                      Fields are similar to READ/WRITE status.

              CPU usage:

                      user, system, context switches, major faults, minor faults

              I/O depths:

                      <=1, 2, 4, 8, 16, 32, >=64

              I/O latencies microseconds:

                      <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000

              I/O latencies milliseconds:

                      <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000

              Disk utilization [v3]:

                      disk name, read ios, write ios, read merges, write merges, read ticks, write ticks, time spent in queue, disk utilization percentage

              Additional Info (dependent on continue_on_error, default off):

                      total # errors, first error code

              Additional Info (dependent on description being set):

                      Text description

       Completion latency percentiles can be a grouping of up to 20 sets, so for the terse output
       fio writes all of them. Each field will look like this:

                 1.00%=6112

       which is the Xth percentile, and the `usec' latency associated with it.

       For  Disk  utilization,  all disks used by fio are shown. So for each disk there will be a
       disk utilization section.

       Below is a single line containing short names for each of the fields in the minimal output
       v3, separated by semicolons:

                 terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util

JSON OUTPUT

       The  json output format is intended to be both human readable and convenient for automated
       parsing. For the most part its sections mirror those of the  normal  output.  The  runtime
       value is reported in msec and the bw value is reported in 1024 bytes per second units.

JSON+ OUTPUT

       The  json+ output format is identical to the json output format except that it adds a full
       dump of the completion latency bins. Each bins object contains a set of (key, value) pairs
       where  keys  are latency durations and values count how many I/Os had completion latencies
       of the corresponding duration. For example, consider:

              "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840"
              :  1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529,
              ... }

       This data indicates that  one  I/O  required  87,552ns  to  complete,  two  I/Os  required
       100,864ns to complete, and 7529 I/Os required 107,008ns to complete.

       Also  included  with  fio is a Python script fio_jsonplus_clat2csv that takes json+ output
       and generates CSV-formatted latency data suitable for plotting.

       The latency durations actually represent the midpoints of latency intervals.  For  details
       refer to `stat.h' in the fio source.

TRACE FILE FORMAT

       There  are  two  trace  file  format  that  you  can  encounter.  The older (v1) format is
       unsupported since version 1.20-rc3 (March 2008). It will still be described below in  case
       that you get an old trace and want to understand it.

       In any case the trace is a simple text file with a single action per line.

       Trace file format v1
              Each line represents a single I/O action in the following format:

                     rw, offset, length

              where  `rw=0/1'  for  read/write,  and  the  `offset' and `length' entries being in
              bytes.

              This format is not supported in fio versions >= 1.20-rc3.

       Trace file format v2
              The second version of the trace file format was  added  in  fio  version  1.17.  It
              allows to access more then one file per trace and has a bigger set of possible file
              actions.

              The first line of the trace file has to be:

                     "fio version 2 iolog"

              Following this can be lines in two different formats, which are described below.

              The file management format:
                     filename action

                     The `filename' is given as an absolute path. The  `action'  can  be  one  of
                     these:

                            add    Add the given `filename' to the trace.

                            open   Open the file with the given `filename'. The `filename' has to
                                   have been added with the add action before.

                            close  Close the file with the given `filename'. The file has to have
                                   been opened before.

              The file I/O action format:
                     filename action offset length

                     The  `filename' is given as an absolute path, and has to have been added and
                     opened before it can be used with this format. The `offset' and `length' are
                     given in bytes. The `action' can be one of these:

                            wait   Wait  for  `offset'  microseconds.  Everything  below  100  is
                                   discarded.  The  time  is  relative  to  the  previous  `wait'
                                   statement.

                            read   Read `length' bytes beginning from `offset'.

                            write  Write `length' bytes beginning from `offset'.

                            sync   fsync(2) the file.

                            datasync
                                   fdatasync(2) the file.

                            trim   Trim  the  given  file  from  the  given `offset' for `length'
                                   bytes.

I/O REPLAY - MERGING TRACES

       Colocation is a common practice used to get the most out  of  a  machine.   Knowing  which
       workloads  play  nicely  with each other and which ones don't is a much harder task. While
       fio can replay workloads concurrently via multiple jobs, it leaves some variability up  to
       the  scheduler  making  results harder to reproduce. Merging is a way to make the order of
       events consistent.

       Merging is integrated into I/O replay and done when a  merge_blktrace_file  is  specified.
       The  list  of  files passed to read_iolog go through the merge process and output a single
       file stored to the specified file. The output file is passed on as if  it  were  the  only
       file passed to read_iolog. An example would look like:

              $ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"

       Creating  only  the  merged  file  can be done by passing the command line argument merge-
       blktrace-only.

       Scaling traces can be done to see the relative impact of any particular trace being slowed
       down  or  sped  up.  merge_blktrace_scalars  takes in a colon separated list of percentage
       scalars. It is index paired with the files passed to read_iolog.

       With scaling, it may be desirable to match the running time of all traces.   This  can  be
       done   with   merge_blktrace_iters.   It   is  index  paired  with  read_iolog  just  like
       merge_blktrace_scalars.

       In an example, given two traces, A and B, each 60s long. If we want to see the  impact  of
       trace  A  issuing  IOs  twice  as fast and repeat trace A over the runtime of trace B, the
       following can be done:

              $  fio   --read_iolog="<trace_a>:"<trace_b>"   --merge_blktrace_file"<output_file>"
              --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"

       This runs trace A at 2x the speed twice for approximately the same runtime as a single run
       of trace B.

CPU IDLENESS PROFILING

       In some cases, we want to understand CPU overhead in a test. For example, we test  patches
       for  the  specific  goodness  of  whether they reduce CPU usage.  Fio implements a balloon
       approach to create a thread per CPU that runs at idle priority, meaning that it only  runs
       when  nobody else needs the cpu.  By measuring the amount of work completed by the thread,
       idleness of each CPU can be derived accordingly.

       An unit work is defined as touching a full page of unsigned characters. Mean and  standard
       deviation of time to complete an unit work is reported in "unit work" section. Options can
       be chosen to report detailed percpu idleness or overall  system  idleness  by  aggregating
       percpu stats.

VERIFICATION AND TRIGGERS

       Fio  is  usually  run  in  one of two ways, when data verification is done. The first is a
       normal write job of some sort with verify enabled. When the write phase has completed, fio
       switches  to  reads and verifies everything it wrote. The second model is running just the
       write phase, and then later on running the same job (but with reads instead of writes)  to
       repeat  the same I/O patterns and verify the contents. Both of these methods depend on the
       write phase being completed, as fio otherwise has no idea how much data was written.

       With verification triggers, fio supports dumping the current write state to  local  files.
       Then a subsequent read verify workload can load this state and know exactly where to stop.
       This is useful for testing cases where power is cut to a server in a managed fashion,  for
       instance.

       A verification trigger consists of two things:

              1) Storing the write state of each job.

              2) Executing a trigger command.

       The  write  state  is  relatively  small,  on  the  order  of  hundreds of bytes to single
       kilobytes. It contains  information  on  the  number  of  completions  done,  the  last  X
       completions, etc.

       A  trigger is invoked either through creation ('touch') of a specified file in the system,
       or through a timeout setting. If fio is run with `--trigger-file=/tmp/trigger-file',  then
       it  will  continually  check  for  the existence of `/tmp/trigger-file'. When it sees this
       file, it will fire off the trigger (thus saving state, and executing the trigger command).

       For client/server runs, there's both a local and remote trigger. If fio is  running  as  a
       server  backend,  it  will  send  the job states back to the client for safe storage, then
       execute the remote trigger, if specified. If a local trigger is specified, the server will
       still send back the write state, but the client will then execute the trigger.

       Verification trigger example
              Let's say we want to run a powercut test on the remote Linux machine 'server'.  Our
              write workload is in `write-test.fio'. We want to cut power  to  'server'  at  some
              point during the run, and we'll run this test from the safety or our local machine,
              'localbox'. On the server, we'll start the fio backend normally:

                     server# fio --server

              and on the client, we'll fire off the workload:

                     localbox$      fio      --client=server       --trigger-file=/tmp/my-trigger
                     --trigger-remote="bash -c "echo b > /proc/sysrq-triger""

              We set `/tmp/my-trigger' as the trigger file, and we tell fio to execute:

                     echo b > /proc/sysrq-trigger

              on  the  server  once it has received the trigger and sent us the write state. This
              will work, but it's not really cutting power to the server,  it's  merely  abruptly
              rebooting  it.  If we have a remote way of cutting power to the server through IPMI
              or similar, we could do that through a local trigger command instead. Let's  assume
              we  have  a  script  that  does  IPMI  reboot  of a given hostname, ipmi-reboot. On
              localbox, we could then have run fio with a local trigger instead:

                     localbox$      fio      --client=server       --trigger-file=/tmp/my-trigger
                     --trigger="ipmi-reboot server"

              For  this  case,  fio  would  wait  for the server to send us the write state, then
              execute `ipmi-reboot server' when that happened.

       Loading verify state
              To load stored  write  state,  a  read  verification  job  file  must  contain  the
              verify_state_load  option.  If  that  is  set,  fio will load the previously stored
              state. For a local fio run this is done by loading the files  directly,  and  on  a
              client/server  run,  the  server backend will ask the client to send the files over
              and load them from there.

LOG FILE FORMATS

       Fio supports a variety of log file formats, for logging latencies,  bandwidth,  and  IOPS.
       The logs share a common format, which looks like this:

              time (msec), value, data direction, block size (bytes), offset (bytes)

       `Time' for the log entry is always in milliseconds. The `value' logged depends on the type
       of log, it will be one of the following:

              Latency log
                     Value is latency in nsecs

              Bandwidth log
                     Value is in KiB/sec

              IOPS log
                     Value is IOPS

       `Data direction' is one of the following:

              0      I/O is a READ

              1      I/O is a WRITE

              2      I/O is a TRIM

       The entry's `block size' is always in bytes. The `offset' is the position  in  bytes  from
       the  start  of  the file for that particular I/O. The logging of the offset can be toggled
       with log_offset.

       Fio defaults to logging every individual I/O but when  windowed  logging  is  set  through
       log_avg_msec,  either  the  average  (by  default)  or  the maximum (log_max_value is set)
       `value' seen over the specified period of time is recorded.  Each  `data  direction'  seen
       within  the window period will aggregate its values in a separate row. Further, when using
       windowed logging the `block size' and `offset' entries will always contain 0.

CLIENT / SERVER

       Normally fio is invoked as a stand-alone application on the machine where the I/O workload
       should  be generated. However, the backend and frontend of fio can be run separately i.e.,
       the fio server can generate an I/O  workload  on  the  "Device  Under  Test"  while  being
       controlled by a client on another machine.

       Start the server on the machine which has access to the storage DUT:

              $ fio --server=args

       where `args' defines what fio listens to. The arguments are of the form `type,hostname' or
       `IP,port'. `type' is either `ip' (or ip4) for TCP/IP v4, `ip6' for TCP/IP  v6,  or  `sock'
       for a local unix domain socket.  `hostname' is either a hostname or IP address, and `port'
       is the port to listen to (only valid for TCP/IP, not a local socket). Some examples:

              1) fio --server
                     Start a fio server, listening on all interfaces on the default port (8765).

              2) fio --server=ip:hostname,4444
                     Start a fio server, listening on IP belonging to hostname and on port 4444.

              3) fio --server=ip6:::1,4444
                     Start a fio server, listening on IPv6 localhost ::1 and on port 4444.

              4) fio --server=,4444
                     Start a fio server, listening on all interfaces on port 4444.

              5) fio --server=1.2.3.4
                     Start a fio server, listening on IP 1.2.3.4 on the default port.

              6) fio --server=sock:/tmp/fio.sock
                     Start a fio server, listening on the local socket `/tmp/fio.sock'.

       Once a server is running, a "client" can connect to the fio server with:

              $ fio <local-args> --client=<server> <remote-args> <job file(s)>

       where `local-args' are arguments for the client where  it  is  running,  `server'  is  the
       connect  string,  and `remote-args' and `job file(s)' are sent to the server. The `server'
       string follows the same format as it does on the server side, to allow  IP/hostname/socket
       and port strings.

       Fio can connect to multiple servers this way:

              $ fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>

       If the job file is located on the fio server, then you can tell the server to load a local
       file as well. This is done by using --remote-config:

              $ fio --client=server --remote-config /path/to/file.fio

       Then fio will open this local (to the server) job file instead of being  passed  one  from
       the client.

       If you have many servers (example: 100 VMs/containers), you can input a pathname of a file
       containing host IPs/names as the parameter value for the  --client  option.  For  example,
       here is an example `host.list' file containing 2 hostnames:

              host1.your.dns.domain
              host2.your.dns.domain

       The fio command would then be:

              $ fio --client=host.list <job file(s)>

       In  this  mode,  you  cannot  input server-specific parameters or job files -- all servers
       receive the same job file.

       In order to let `fio --client' runs use a shared  filesystem  from  multiple  hosts,  `fio
       --client'  now  prepends the IP address of the server to the filename. For example, if fio
       is using the directory  `/mnt/nfs/fio'  and  is  writing  filename  `fileio.tmp',  with  a
       --client   `hostfile'   containing   two   hostnames  `h1'  and  `h2'  with  IP  addresses
       192.168.10.120 and 192.168.10.121, then fio will create two files:

              /mnt/nfs/fio/192.168.10.120.fileio.tmp
              /mnt/nfs/fio/192.168.10.121.fileio.tmp

AUTHORS

       fio was written by Jens Axboe <axboe@kernel.dk>.
       This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au> based on documentation
       by Jens Axboe.
       This man page was rewritten by Tomohiro Kusumi <tkusumi@tuxera.com> based on documentation
       by Jens Axboe.

REPORTING BUGS

       Report bugs to the fio mailing list <fio@vger.kernel.org>.
       See REPORTING-BUGS.

       REPORTING-BUGS: http://git.kernel.dk/cgit/fio/plain/REPORTING-BUGS

SEE ALSO

       For further documentation see HOWTO and README.
       Sample jobfiles are available in the `examples/' directory.
       These are typically located under `/usr/share/doc/fio'.

       HOWTO: http://git.kernel.dk/cgit/fio/plain/HOWTO
       README: http://git.kernel.dk/cgit/fio/plain/README