Provided by: fio_3.16-1_amd64 bug


       fio - flexible I/O tester


       fio [options] [jobfile]...


       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.


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

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

              Write output to filename.

              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.

              Generate aggregate bandwidth logs.

              Print statistics in a terse, semicolon-delimited format.

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

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

              Print version information and exit.

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

              Perform test and validation of internal CPU clock.

              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.

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

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

              Convert jobfile to a set of command-line options.

              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.

              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.

              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.

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

              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.

              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.

              Allocate additional internal smalloc pools of size  kb  in  KiB.  The  --alloc-size
              option  increases  shared  memory  set aside for use by fio.  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'.

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

              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.

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

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

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

              Tell fio server to load this local file.

              Report CPU idleness. option is one of the following:

                            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 and output compressed log.

              Execute trigger command when file exists.

              Execute trigger at this time.

              Set this command as local trigger.

              Set this command as remote trigger.

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


       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.

       Note that the maximum length of a line in the job file is 8192 bytes.


       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).


       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

                     [*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

              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

                     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.

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


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

              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

              Base unit for reporting. Allowed values are:

                     0      Use auto-detection (default).

                     8      Byte based.

                     1      Bit based.

   Job description
              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.

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

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

              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
              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.

              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.

              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.

              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.

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



                     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.

              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

              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
              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

              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

              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

              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.

              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:

                            The name of the worker thread or process.

                            The incremental number of the worker thread or process.

                            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.

              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.

              Recursively open any files below directory 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.

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

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

              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.

              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.

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

                     random Choose a file at random.

                            Round robin over opened files. This is the default.

                            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.

              Attempt to switch the device hosting the file to the specified I/O scheduler before

              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.

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

              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

              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.

              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.

              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.

              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 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 job files after each iteration or loop. Default: false.

              Accepted values are:

                     none   The zonerange, zonesize and zoneskip parameters are ignored.

                            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.

              For zonemode=strided, this is the size of a single  zone.  See  also  zonesize  and

              For zonemode=zbd, this parameter is ignored.

              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. For a job accessing  a  zoned  block  device,  the  specified
              zonesize  must be 0 or equal to the device zone size. For a regular block device or
              file, the specified zonesize must be at least 512B.

              For zonemode=strided, the number of bytes to skip after zonesize bytes of data have
              been transferred.

              For zonemode=zbd, the zonesize aligned number of bytes to skip once a zone is fully
              written (write workloads) or all written data in the  zone  have  been  read  (read
              workloads).  This  parameter is valid only for sequential workloads and ignored for
              random workloads. For read workloads, see also read_beyond_wp.

              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 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.

              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.

              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

              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
              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.

              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.

              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

                            Random reads.

                            Random writes.

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

                            Sequential mixed reads and writes.

                     randrw Random mixed reads and writes.

                            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.

              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:

                            Generate sequential offset.

                            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.

              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.

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

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

              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.

              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.

              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.

                            Advise using FADV_SEQUENTIAL.

                     random Advise using FADV_RANDOM.

              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.

                            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.

              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%.

              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.

              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.
              Percentages can be used for this option.  If a percentage is given,  the  generated
              offset  will be aligned to the minimum blocksize or to the value of offset_align if

              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.

              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.

              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.

              Make every N-th write a barrier write.

              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:


                     write  SYNC_FILE_RANGE_WRITE


              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.

              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:

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

              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:

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

              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.

              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

              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

                     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:


              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:


              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.

              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.

              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.

              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.

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

                            Strong 2^88 cycle random number generator.

                     lfsr   Linear feedback shift register generator.

                            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.

                     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

       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.


              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:


              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:


              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:


              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:


              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.

              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
              Initialize buffers with all zeros. Default: fill buffers with random data.

              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.

              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.

              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.

              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

              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


              Also you can combine everything together in any order:


              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 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.

              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).

                            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'.

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

                            Same as mmap, but use a MMAP_SHARED mapping.

                            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.

              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.

              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
              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.

              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.

              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
              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.

                            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.

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

                            Solaris native asynchronous I/O.

                            Windows native asynchronous I/O. Default on Windows.

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

                     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.

                            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
                   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            =

                            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.

                            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

                            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

                            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.

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

                            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.

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

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

                            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.

                            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.

                            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.

                            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

                            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.

                            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

                            Read and write iscsi lun with libiscsi.

                     nbd    Synchronous read and write a Network Block Device (NBD).

   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.

              If  this  option  is  set, fio will attempt to use polled IO completions. Normal IO
              completions generate interrupts to signal the completion of IO, polled  completions
              do not. Hence they are require active reaping by the application.  The benefits are
              more efficient IO for high IOPS scenarios, and lower latencies for low queue  depth

              If  fio  is  asked to do direct IO, then Linux will map pages for each IO call, and
              release them when IO is done. If this option  is  set,  the  pages  are  pre-mapped
              before  IO  is  started.  This  eliminates the need to map and release for each IO.
              This is more efficient, and reduces the IO latency as well.

              With this option, fio registers the set of files being used with the kernel.   This
              avoids  the  overhead  of managing file counts in the kernel, making the submission
              and completion part more lightweight. Required for the below sqthread_poll option.

              Normally fio will submit IO by issuing a  system  call  to  notify  the  kernel  of
              available  items  in  the  SQ ring. If this option is set, the act of submitting IO
              will be done by a polling thread in the kernel. This frees up cycles  for  fio,  at
              the cost of using more CPU in the system.

              When  `sqthread_poll` is set, this option provides a way to define which CPU should
              be used for the polling thread.

              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').

              Set  RWF_HIPRI  on  I/O, indicating to the kernel that it's of higher priority than

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

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

              Split the load into cycles of the given time. In microseconds.

              Detect when I/O threads are done, then exit.

              The hostname or IP address of a HDFS cluster namenode to contact.

              The listening port of the HFDS cluster namenode.

              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.

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

              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.

              The IP address of the network interface used to send or receive UDP multicast.

              Time-to-live value for outgoing UDP multicast packets. Default: 1.

              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.

              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.

              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.

              Set the desired socket buffer size for the connection.

              Set the TCP maximum segment size (TCP_MAXSEG).

              File will be used as a block donor (swap extents between files).

              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.

              Specifies the name of the Ceph cluster.

              Specifies the name of the RBD.

              Specifies the name of the Ceph pool containing RBD or RADOS data.

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

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

              Hostname to connect to. For S3, this could be the bucket name. Default is localhost

              Username for HTTP authentication.

              Password for HTTP authentication.

              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.

              Which HTTP access mode to use: webdav, swift, or s3. Default is webdav.

              The S3 region/zone to include in the request. Default is us-east-1.

              The S3 secret key.

              The S3 key/access id.

              The Swift auth token. See the example configuration file on how to retrieve this.

              Enable  verbose  requests  from  libcurl.  Useful for debugging. 1 turns on verbose
              logging from libcurl, 2 additionally enables HTTP IO tracing.  Default is 0

              Skip operations against known bad blocks.

              libhdfs will create chunk in this HDFS directory.

              The size of the chunk to use for each file.

              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.

              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.

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

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

              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.

              Specify the NBD URI of the server to test.  The string is a standard NBD  URI  (see
      Example URIs:




   I/O depth
              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

       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.

              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:


              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:


              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.

              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  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.

              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
              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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 ( The lambda  will  be
              10^6 / IOPS for the given workload.

              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
              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

              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.

              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.

              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.

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

   I/O replay
              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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

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

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

   Threads, processes and job synchronization
              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.

              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).

              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.

              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.

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

              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

              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.

              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.

              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

              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.

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


              `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'.

              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

              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.

              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.

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

              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.

              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.

              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.

              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.

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

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

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

              Set group ID, see uid.

              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.

              Run the verify phase after a write phase. Only valid if  verify  is  set.  Default:

              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

                     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.

                            Synonym for crc32c.

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

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

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

                     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.

                            Use optimized sha3-224 as the checksum function.

                            Use optimized sha3-256 as the checksum function.

                            Use optimized sha3-384 as the checksum function.

                            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.

                            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.

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

              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

              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.:


              Or use combination of everything:


              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.

              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.

              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.

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

              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.

              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.

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

              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.

              Number of verify blocks to discard/trim.

              Verify that trim/discarded blocks are returned as zeros.

              Verify that trim/discarded blocks are returned as zeros.

              Trim this number of I/O blocks.

              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).

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

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

                                   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
              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.

              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.

              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.

              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.

              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


              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

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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.

              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

              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.

              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.

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

              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 measurements of completion latency numbers. See disable_lat.

              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.

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

              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.

              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.

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

              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'.

              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.


              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.

              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.

              The predefined workload to run. Current profiles are:

                            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

              $ fio --profile=act --cmdhelp

   Act profile options
              Devices to use.

              ACT load multiplier. Default: 1.

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

              Number of read I/O threads per device. Default: 8.

              Number of 512B blocks to read at the time. Default: 3.

              Size of large block ops in KiB (writes). Default: 131072.

       prep   Set to run ACT prep phase.

   Tiobench profile options
              Size in MiB.

              Block size in bytes. Default: 4096.

              Number of runs.

              Test directory.

              Number of threads.


       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

                 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:

                     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

                 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

                   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.

                     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.


       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:

                 A description of this job goes here.

       The  job  description  (if provided) follows on a second line for terse v2.  It appears on
       the same line for other terse versions.

       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:


       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:


       In client/server mode terse output differs from what appears when jobs  are  run  locally.
       Disk  utilization  data  is  omitted  from  the standard terse output and for v3 and later
       appears on its own separate line at the end of each terse reporting cycle.


       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.


       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.


       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

              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

              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

                            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'

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

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

                            sync   fsync(2) the file.

                                   fdatasync(2) the file.

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


       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-

       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

       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.


       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.


       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

       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.


       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.


       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=
                     Start a fio server, listening on IP 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:


       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 and, then fio will create two files:


       Terse  output in client/server mode will differ slightly from what is produced when fio is
       run in stand-alone mode. See the terse output section for details.


       fio was written by Jens Axboe <>.
       This man page was written by Aaron Carroll <> based on documentation
       by Jens Axboe.
       This man page was rewritten by Tomohiro Kusumi <> based on documentation
       by Jens Axboe.


       Report bugs to the fio mailing list <>.



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