Provided by: fio_2.2.10-1ubuntu1_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  of  various  fio  actions.  May be `all' for all types or
              individual types separated by a comma (eg --debug=io,file). `help'  will  list  all
              available tracing options.

              Write output to filename.

              Set the reporting format to normal, terse, or json.

              Limit run time to runtime seconds.

              Generate per-job bandwidth logs.

              Print statistics in a terse, semicolon-delimited format.

              Print statistics in selected mode AND terse, semicolon-delimited format.

              Display version information and exit.

              Set terse version output format (Current version 3, or older version 2).

       --help Display usage information and exit.

              Perform test and validation of internal CPU clock

              Test  the speed of the builtin checksumming functions. If no argument is given, all
              of them are tested. Or 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

              Convert jobfile to a set of command-line options.

              Specifies when real-time ETA estimate should  be  printed.   when  may  be  one  of
              `always', `never' or `auto'.

              Force an ETA newline for every `time` period passed.

              Report full output status every `time` period passed.

              Turn on safety read-only checks, preventing any attempted write.

              Only  run  section sec from job file. This option can be used multiple times to add
              more sections to run.

              Set the internal smalloc pool size to kb kilobytes.

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

              Set the maximum allowed number of jobs (threads/processes) to support.

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

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

              Instead  of running the jobs locally, send and run them on the given host or set of
              hosts.  See client/server section.

              Report cpu idleness on a system or percpu basis (option=system,percpu) or run  unit
              work calibration only (option=calibrate).


       Job  files  are  in `ini' format. They consist of one or more job definitions, which begin
       with a job name in square brackets and extend to the next job name.  The job name  can  be
       any  ASCII string except `global', which has a special meaning.  Following the job name is
       a sequence of zero or more parameters, one per line, that define the behavior of the  job.
       Any line starting with a `;' or `#' character is considered a comment and ignored.

       If jobfile is specified as `-', the job file will be read from standard input.

   Global Section
       The  global section contains default parameters for jobs specified in the job file.  A job
       is only affected by global sections residing above it, and there  may  be  any  number  of
       global  sections.   Specific  job  definitions  may  override  any parameter set in global


       Some parameters may take arguments of a  specific  type.   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 types used are:

       str    String: a sequence of alphanumeric characters.

       int    SI  integer: a whole number, possibly containing a suffix denoting the base unit of
              the value.  Accepted suffixes are `k',  'M',  'G',  'T',  and  'P',  denoting  kilo
              (1024),   mega   (1024^2),   giga   (1024^3),  tera  (1024^4),  and  peta  (1024^5)
              respectively.  If  prefixed  with  '0x',  the  value  is  assumed  to  be  base  16
              (hexadecimal).  A suffix may include a trailing 'b', for instance 'kb' is identical
              to 'k'. You can specify a base 10 value by using 'KiB', 'MiB','GiB', etc.  This  is
              useful  for  disk drives where values are often given in base 10 values. Specifying
              '30GiB' will get you 30*1000^3 bytes.  When specifying  times  the  default  suffix
              meaning  changes,  still denoting the base unit of the value, but accepted suffixes
              are 'D' (days), 'H' (hours), 'M' (minutes),  'S'  Seconds,  'ms'  (or  msec)  milli
              seconds,  'us'  (or  'usec')  micro  seconds.  Time  values  without a unit specify
              seconds.  The suffixes are not case sensitive.

       bool   Boolean: a true or false value. `0' denotes false, `1' denotes true.

       irange Integer range:  a  range  of  integers  specified  in  the  format  lower:upper  or
              lower-upper. lower and upper may contain a suffix as described above.  If an option
              allows two sets of ranges, they are separated with a  `,'  or  `/'  character.  For
              example: `8-8k/8M-4G'.

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

   Parameter List
              May  be used to override the job name.  On the command line, this parameter has the
              special purpose of signalling the start of a new job.

              Human-readable description of the job. It is printed  when  the  job  is  run,  but
              otherwise has no special purpose.

              Prefix filenames with this directory.  Used to place files in a location other 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
              creates with 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 each clone if not specified, but  let
              all  clones use the same if set. See filename for considerations regarding escaping
              certain characters on some platforms.

              fio normally makes up a file name based on the job name, thread  number,  and  file
              number.  If  you  want  to  share  files  between threads in a job or several jobs,
              specify a filename for each of them to override the default.  If the I/O engine  is
              file-based,  you  can  specify a number of files by separating the names with a `:'
              character. `-' is a reserved name,  meaning  stdin  or  stdout,  depending  on  the
              read/write direction set. 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). If the wanted filename does need to include a colon, then escape that
              with  a  '\' character. For instance, if the filename is "/dev/dsk/foo@3,0:c", then
              you would use filename="/dev/dsk/foo@3,0\:c".

              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.

              Fio defaults to not locking any files before it does IO to them. If a file or  file
              descriptor  is  shared,  fio  can  serialize IO 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. This is the default.

                            Only one thread or process may do IO at a time, excluding all others.

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

       opendir=str Recursively open any files below directory str.

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

                     read   Sequential reads.

                     write  Sequential writes.

                     trim   Sequential trim (Linux block devices only).

                            Random reads.

                            Random writes.

                            Random trim (Linux block devices only).

                     rw, readwrite
                            Mixed sequential reads and writes.

                     randrw Mixed random reads and writes.

                            Trim and write mixed workload. Blocks will be trimmed first, then the
                            same blocks will be written to.

              For  mixed  I/O, the default split is 50/50. For certain types of io the result may
              still be skewed a bit, since the speed may be different. It is possible to  specify
              a  number  of  IO's  to do before getting a new offset, this is done by appending a
              `:<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 postfix
              is used with a sequential IO pattern, then the value specified will be added to the
              generated  offset  for  each  IO.  For instance, using rw=write:4k will skip 4k for
              every write. It turns  sequential  IO  into  sequential  IO  with  holes.  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  IO  offset  being  generated.
              Accepted values are:

                            Generate sequential offset

                            Generate the same offset

              sequential  is  only  useful for random IO, where fio would normally generate a new
              random offset for every IO. If you append eg 8 to randread, you  would  get  a  new
              random  offset  for every 8 IO's. The result would be a seek for only every 8 IO's,
              instead of for every IO. Use rw=randread:8 to specify that.  As  sequential  IO  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.

              The   base  unit  for  a  kilobyte.  The  defacto  base  is  2^10,  1024.   Storage
              manufacturers like to use 10^3 or 1000 as a base  ten  unit  instead,  for  obvious
              reasons. Allowed values are 1024 or 1000, with 1024 being the default.

              Fio  normally  reports statistics on a per data direction basis, meaning that read,
              write, and trim are accounted and reported separately. If this option  is  set  fio
              sums the results and reports 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.

                     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 must be set to 'none' because ZFS doesn't support  it.
              Default: 'posix'.

              Use  posix_fadvise(2)  to  advise  the  kernel  what  I/O patterns are likely to be
              issued. Default: true.

              Use posix_fadvise(2) to advise the kernel what stream ID the writes  issued  belong
              to. Only supported on Linux. Note, this option may change going forward.

              Total  size  of  I/O  for  this  job.  fio will run until this many bytes have been
              transferred,  unless  limited  by  other  options  (runtime,   for   instance,   or
              increased/descreased  by  io_size).  Unless nrfiles and filesize options are given,
              this amount will be divided between the available files for the job.  If  not  set,
              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.

       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 IO to be performed.  Sometimes that is not
              what you want. With this option, it is possible to define just  the  amount  of  IO
              that  fio should do. For instance, if size is set to 20G and io_limit is set to 5G,
              fio will perform IO within the first 20G but exit  when  5G  have  been  done.  The
              opposite  is also possible - if size is set to 20G, and io_size is set to 40G, then
              fio will do 40G of IO within the 0..20G region.

       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 IO 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.

              Individual  file  sizes.  May  be  a range, in which case fio will select sizes for
              files at random within the given range, limited  to  size  in  total  (if  that  is
              given). If filesize is not specified, each created file is the same size.

              Perform  IO 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.

       blocksize=int[,int], bs=int[,int]
              Block size for I/O units.  Default: 4k.  Values for reads, writes, and trims can be
              specified  separately in the format read,write,trim either of which may be empty to
              leave that value at its default. If a trailing comma  isn't  given,  the  remainder
              will inherit the last value set.

       blocksize_range=irange[,irange], bsrange=irange[,irange]
              Specify  a range of I/O block sizes.  The issued I/O unit will always be a multiple
              of the minimum size, unless blocksize_unaligned is set.  Applies to both reads  and
              writes  if  only  one  range is given, but can be specified separately with a comma
              separating the values. Example: bsrange=1k-4k,2k-8k.  Also (see blocksize).

              This option allows even finer grained control of the block sizes issued,  not  just
              even  splits between them. With this option, you can weight various block sizes for
              exact control of the issued IO for a job that has mixed block sizes. The format  of
              the  option  is bssplit=blocksize/percentage, optionally adding as many definitions
              as needed separated by a colon.  Example: bssplit=4k/10:64k/50:32k/40  would  issue
              50%  64k  blocks,  10%  4k  blocks and 40% 32k blocks. bssplit also supports giving
              separate splits to reads and writes. The format is identical to what the bs  option
              accepts, the read and write parts are separated with a comma.

       blocksize_unaligned, bs_unaligned
              If  set,  any  size in blocksize_range may be used.  This typically won't work with
              direct I/O, as that normally requires sector alignment.

       blockalign=int[,int], ba=int[,int]
              At what boundary to align random IO offsets. Defaults to the  same  as  'blocksize'
              the  minimum blocksize given.  Minimum alignment is typically 512b for using direct
              IO, 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.

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

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

              If  this  option  is  given,  fio  will  refill the IO 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 IO 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 IO buffer content (on WRITEs) that
              compress to the specified level. Fio does this by providing a mix  of  random  data
              and  a  fixed pattern. The fixed pattern is either zeroes, or the pattern specified
              by buffer_pattern. If the pattern option is used, it  might  skew  the  compression
              ratio  slightly.  Note  that  this  is  per  block  size  unit,  for file/disk wide
              compression level that matches this setting. Note that this is per block size unit,
              for file/disk wide compression level that matches this setting, you'll also want to
              set refill_buffers.

              See buffer_compress_percentage. This setting allows  fio  to  manage  how  big  the
              ranges  of  random  data  and  zeroed  data  is. Without this set, fio will provide
              buffer_compress_percentage of blocksize random  data,  followed  by  the  remaining
              zeroed.  With  this  set  to  some  chunk size smaller than the block size, fio can
              alternate random and zeroed data throughout the IO buffer.

              If set, fio will fill the IO buffers with this pattern. If not set, the contents of
              IO  buffers is 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 "", e.g.:

              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.

              Number of files to use for this job.  Default: 1.

              Number of files to keep open at the same time.  Default: nrfiles.

              Defines how files to service are selected.  The following types are defined:

                     random Choose a file at random.

                            Round robin over opened files (default).

                            Do each file in the set sequentially.

              The  number  of  I/Os  to  issue before switching to a new file can be specified by
              appending `:int' to the service type.

              Defines how the job issues I/O.  The following types are defined:

                     sync   Basic read(2) or write(2) I/O.  fseek(2) is used to position the  I/O

                     psync  Basic pread(2) or pwrite(2) I/O.

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

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

                     libaio Linux native asynchronous I/O. This ioengine defines engine  specific

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

                            Solaris native asynchronous I/O.

                            Windows native asynchronous I/O.

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

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

                            Use the syslet system calls to make regular read/write asynchronous.

                     sg     SCSI generic sg v3 I/O. May be either  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.

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

                     net    Transfer  over  the  network.  The protocol to be used can be defined
                            with the protocol parameter.  Depending on  the  protocol,  filename,
                            hostname,  port,  or listen must be specified.  This ioengine defines
                            engine specific options.

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

                     cpuio  Doesn't  transfer any data, but burns CPU cycles according to cpuload
                            and cpucycles parameters.

                     guasi  The GUASI I/O engine is the Generic  Userspace  Asynchronous  Syscall
                            Interface approach to asynchronous I/O.
                            See <>.

                     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.

                            Loads an external I/O engine object file.  Append the engine filename
                            as `:enginepath'.

                               IO engine  that  does  regular  linux  native  fallocate  call  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            =

                            IO engine that does  regular  EXT4_IOC_MOVE_EXT  ioctls  to  simulate
                            defragment activity request to DDIR_WRITE event

                     rbd    IO  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.

                     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,  libhdfs engine expects bunch of small files to be created over
                            HDFS, and engine will randomly pick a file out of those  files  based
                            on  the offset generated by fio backend. (see the example job file to
                            create such files, use rw=write option). Please note, you might  want
                            to  set  necessary  environment  variables  to work with hdfs/libhdfs

                     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 writetrim mode works well for this constraint.

              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 degress
              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 IO is not async on that OS. Keep an eye on
              the IO depth distribution in the fio output to verify that the achieved depth is as
              expected. Default: 1.

              Number of I/Os to submit at once.  Default: iodepth.

              This defines how many pieces of IO to retrieve at once. It defaults to 1 which
               means that we'll ask for a minimum of 1 IO  in  the  retrieval  process  from  the
              kernel.  The  IO 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 IO. This helps reduce IO latency, at the cost of more retrieval system

              Low watermark indicating when to start filling the queue again.  Default: iodepth.

              This option controls how fio submits the IO  to  the  IO  engine.  The  default  is
              inline,  which  means that the fio job threads submit and reap IO directly.  If set
              to offload, the job threads will offload IO submission to a dedicated  pool  of  IO
              threads.  This  requires  some  coordination  and thus has a bit of extra overhead,
              especially for lower queue depth IO 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 IO gets back up on  the  device  side  (the
              coordinated omission problem).

              If true, use non-buffered I/O (usually O_DIRECT).  Default: false.

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

              If true, use buffered I/O.  This is the opposite of the direct parameter.  Default:

              Offset in the file to start I/O. Data before the offset will not be touched.

              If this is provided, then the real offset becomes the 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.

              Fio will normally perform IOs 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 IOs  to  perform.
              When  fio  reaches  this number, it will exit normally and report status. Note that
              this does not extend the amount of IO that will be done, it will only stop  fio  if
              this condition is met before other end-of-job criteria.

              How  many  I/Os  to  perform before issuing an fsync(2) of dirty data.  If 0, don't
              sync.  Default: 0.

              Like fsync, but uses fdatasync(2) instead to only sync the data parts of the  file.
              Default: 0.

              Make every Nth write a barrier write.

              Use  sync_file_range(2)  for  every  val 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 writing, setup the file first and do overwrites.  Default: false.

              Sync file contents when a write stage has completed.  Default: false.

              If true, sync file contents on close.  This differs from end_fsync in that it  will
              happen on every close, not just at the end of the job.  Default: false.

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

              Percentage  of a mixed workload that should be writes.  If rwmixread and rwmixwrite
              are given and do not sum to 100%, the latter of the two overrides 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 IO. 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

              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, 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 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. It is possible
              to  set  different values for reads, writes, and trim. To do so, simply use a comma
              separated list. See blocksize.

              Normally fio will cover every block of the file when  doing  random  I/O.  If  this
              parameter  is  given,  a  new  offset  will  be  chosen without looking at past I/O
              history.  This parameter is mutually exclusive with verify.

              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 IO offsets for random IO:

                     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
              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 IO
              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.

              Run job with given nice value.  See nice(2).

              Set  I/O  priority  value  of  this  job  between  0 (highest) and 7 (lowest).  See

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

              Stall job for given number of microseconds between issuing I/Os.

              Pretend to spend CPU time for given number of microseconds, sleeping  the  rest  of
              the time specified by thinktime.  Only valid if thinktime is set.

              Only  valid  if thinktime is set - control how many blocks to issue, before waiting
              thinktime microseconds. If not  set,  defaults  to  1  which  will  make  fio  wait
              thinktime  microseconds  after  every block. This effectively makes any queue depth
              setting redundant, since no more than 1  IO  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.  Default: 1.

              Cap bandwidth used by this job. The number is  in  bytes/sec,  the  normal  postfix
              rules  apply.  You can use rate=500k to limit reads and writes to 500k each, or you
              can specify read and writes separately. Using rate=1m,500k  would  limit  reads  to
              1MB/sec  and  writes  to  500KB/sec.  Capping only reads or writes can be done with
              rate=,500k or rate=500k,. The former will only limit  writes  (to  500KB/sec),  the
              latter will only limit reads.

              Tell  fio  to do whatever it can to maintain at least the given bandwidth.  Failing
              to meet this requirement will cause the job to exit. The same  format  as  rate  is
              used for read vs write separation.

              Cap  the  bandwidth  to  this  number  of  IOPS.  Basically  the same as rate, just
              specified independently of bandwidth. The same format as rate is used for  read  vs
              write  separation.  If blocksize is a range, the smallest block size is used as the

              If this rate of I/O is not met, the job will exit. The same format as rate is  used
              for read vs write separation.

              Average  bandwidth for rate and ratemin over this number of milliseconds.  Default:

              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. The values is given in
              microseconds. See latency_window and latency_percentile.

              Used with latency_target to specify the sample  window  that  the  job  is  run  at
              varying queue depths to test the performance. The value is given in microseconds.

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

              If set, fio will exit the job if it exceeds this maximum latency. It will exit with
              an ETIME error.

              Set CPU affinity for this job. int is a bitmask of allowed CPUs the job may run on.
              See sched_setaffinity(2).

              Same as cpumask, but allows a comma-delimited list of CPU numbers.

              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 behaviour,  if  the  option  isn't  specified.  If  split  is
              specified,  then  fio 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 this job running on specified NUMA  nodes'  CPUs.  The  arguments  allow  comma
              delimited list of cpu numbers, A-B ranges, or 'all'.

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


              mode   is one of the following memory policy:

              default, prefer, bind, interleave, local

              For default and local memory policy, no nodelist is
              needed  to  be  specified.  For  prefer,  only  one  node  is allowed. For bind and
              interleave, nodelist allows comma delimited list of numbers, A-B ranges, or 'all'.

              Delay start of job for the specified number of seconds. Supports all time  suffixes
              to  allow  specification  of hours, minutes, seconds and milliseconds - seconds are
              the default if a unit is omitted.  Can be given as a range which causes each thread
              to choose randomly out of the range.

              Terminate processing after the specified number of seconds.

              If  given,  run for the specified runtime duration even if the files are completely
              read or written. The same workload will  be  repeated  as  many  times  as  runtime

              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.

              Invalidate buffer-cache for the file prior to starting I/O.  Default: true.

              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
              Allocation method for I/O unit buffer.  Allowed values are:

                     malloc Allocate memory with malloc(3).

                     shm    Use shared memory buffers allocated through shmget(2).

                            Same as shm, but use huge pages as backing.

                     mmap   Use mmap(2) for allocation.  Uses anonymous memory unless a  filename
                            is given after the option in the format `:file'.

                            Same as mmap, but use huge files as backing.

              The  amount  of  memory  allocated  is  the  maximum  allowed blocksize for the job
              multiplied by iodepth.  For shmhuge or mmaphuge to work, the system must have  free
              huge pages allocated.  mmaphuge also needs to have hugetlbfs mounted, and file must
              point there. At least  on  Linux,  huge  pages  must  be  manually  allocated.  See
              /proc/sys/vm/nr_hugehages and the documentation for that. Normally you just need to
              echo an appropriate number, eg echoing 8 will ensure that the OS has 8  huge  pages
              ready for use.

       iomem_align=int, mem_align=int
              This  indicates  the memory alignment of the IO memory buffers. Note that the given
              alignment is applied to the first IO 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 IO
              memory buffers is the sum of the iomem_align and bs used.

              Defines the size of a huge page.  Must be at least equal  to  the  system  setting.
              Should be a multiple of 1MB. Default: 4MB.

              Terminate all jobs when one finishes.  Default: wait for each job to finish.

              Average  bandwidth  calculations  over  the  given  time in milliseconds.  Default:

              Average IOPS calculations over the given time in milliseconds.  Default: 500ms.

              If true, serialize file creation for the jobs.  Default: true.

              fsync(2) data file after creation.  Default: true.

              If true, the files are not created until they are opened for IO by 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

              If true, fio is permitted to create files as part of  its  workload.  This  is  the
              default  behavior. 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 (eg 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. Default: false.

              If  this  is given, files will be pre-read into memory before starting the given IO
              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 IO engines that are seekable,
              since they allow you to read the same data multiple times. Thus it will not work on
              eg network or splice IO.

              Unlink job files when done.  Default: false.

              Specifies  the  number  of  iterations  (runs  of  the  same workload) of this job.
              Default: 1.

              Do not perform the 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:

              Method  of  verifying  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=str can be combined with verify_pattern=str option.  The allowed values are:

                     md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256 sha512 sha1 xxhash
                            Store appropriate checksum in the header of each block.  crc32c-intel
                            is  hardware  accelerated SSE4.2 driven, falls back to regular crc32c
                            if not supported by the system.

                     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=str
                            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   Pretend to verify.  Used for testing internals.

              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.

              If true, written verify blocks are sorted if fio deems it to be faster to read them
              back in a sorted manner.  Default: true.

              Pre-load and sort verify blocks for a read workload.

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

              Write the verification header  for  this  number  of  bytes,  which  should  divide
              blocksize.  Default: blocksize.

              If  set,  fio  will  fill the io buffers with this pattern. Fio defaults to filling
              with totally random bytes, but sometimes it's interesting  to  fill  with  a  known
              pattern  for  io  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=str.   Also,
              verify_pattern  supports  %o format, which means that for each block offset will be
              written and then verifyied back, e.g.:
              Or use combination of everything:


              If true, exit the job on the first observed verification 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 IO inline from the submitting thread. This option takes an
              integer  describing  how  many  async offload threads to create for IO verification
              instead, causing fio to offload the duty of verifying IO contents to  one  or  more
              separate  threads.   If using this offload option, even sync IO engines can benefit
              from using an iodepth setting higher than 1, as it allows them to have IO in flight
              while verifies are running.

              Tell  fio  to set the given CPU affinity on the async IO 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 IO 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.

              Number of verify blocks to discard/trim.

              Verify that trim/discarded blocks are returned as zeroes.

              Trim after this number of blocks are written.

              Trim this number of IO blocks.

              Enable experimental verification.

              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.

              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.

       stonewall , wait_for_previous
              Wait  for  preceding  jobs  in  the  job  file  to  exit  before starting this one.
              stonewall implies new_group.

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

              Number  of  clones  (processes/threads  performing  the same workload) of this job.
              Default: 1.

              If set, display per-group reports instead of per-job when numjobs is specified.

       thread Use threads created  with  pthread_create(3)  instead  of  processes  created  with

              Divide file into zones of the specified size in bytes.  See zoneskip.

              Give size of an IO zone.  See zoneskip.

              Skip the specified number of bytes when zonesize bytes of data have been read.

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

              Replay the I/O patterns contained in the specified file generated  by  write_iolog,
              or may be a blktrace binary file.

              While  replaying  I/O  patterns  using  read_iolog the default behavior attempts to
              respect timing information between I/Os.  Enabling replay_no_stall causes  I/Os  to
              be replayed as fast as possible while still respecting ordering.

              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.   Setting
              replay_redirect  causes  all  IOPS  to be replayed onto the single specified device
              regardless of the device it was recorded from.

              Force alignment of IO offsets and lengths in a trace to this power of 2 value.

              Scale sector offsets down by this factor when replaying traces.

              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.

              If  given, write a bandwidth log of the jobs in this job file. Can be used to store
              data  of  the  bandwidth  of   the   jobs   in   their   lifetime.   The   included
              fio_generate_plots  script  uses gnuplot to turn these text files into nice graphs.
              See write_lat_log for behaviour of given filename. For this option, the postfix  is
              _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 job index.

              Same as write_bw_log, but writes I/O completion latencies.  If no filename is given
              with  this option, the default filename of "jobname_type.x.log" is used, where x is
              the index of the job (1..N, where N is the number of jobs). Even if the filename is
              given,  fio  will  still append the type of log. If per_job_logs is false, then the
              filename will not include the job index.

              Same as write_bw_log, but writes IOPS. If no filename is given  with  this  option,
              the  default  filename of "jobname_type.x.log" is used, where x is the index of the
              job (1..N, where N is the number of jobs). Even if the filename is given, fio  will
              still  append the type of log. If per_job_logs is false, then the filename will not
              include the job index.

              By default, fio will log an entry in the iops, latency, or bw log for every IO 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.  Defaults to 0.

              If  this is set, the iolog options will include the byte offset for the IO entry as
              well as the other data values.

              If this is set, fio will compress the IO 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 IO 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 IO 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.

              If set, and log_compression is also  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, 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

              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 as well.

              Disable measurements of completion latency numbers. See disable_lat.

              Disable measurements of submission latency numbers. See disable_lat.

              Disable measurements of throughput/bandwidth numbers. See disable_lat.

              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.

              Before running the job, execute the specified command with system(3).
              Output is redirected in a file called jobname.prerun.txt

              Same as exec_prerun, but the command is executed after the job completes.
              Output is redirected in a file called jobname.postrun.txt

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

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

              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) 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
              gtod() calls we would have done if all time keeping was enabled.

              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 IO 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.

              Sometimes  you  want to ignore some errors during test in that case you can specify
              error list for each error type.
              errors for given error type is separated with ':'.  Error may be symbol  ('ENOSPC',
              'ENOMEM') or an integer.
              Example: ignore_error=EAGAIN,ENOSPC:122 .
              This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from WRITE.

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

              Select a specific builtin performance test.

              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

              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.

              Base unit for reporting.  Allowed values are:

              0      Use auto-detection (default).

              8      Byte based.

              1      Bit based.

              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

              Enable the reporting of percentiles of completion latencies.

              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.  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.

   Ioengine Parameters List
       Some parameters 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.

              Attempt to use the specified percentage of CPU cycles.

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

              Detect when IO threads are done, then exit.

              Normally, with the libaio engine in use, fio will use the io_getevents 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 (eg when iodepth_batch_complete=0).

              The  host  name  or IP address to use for TCP or UDP based IO.  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 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  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.

       (net,netsplice)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  packets.  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 block allocation strategy
              0(default): Preallocate donor's file on init

              1:     allocate  space  immediately  inside  defragment event, and free right after

              Specifies the name of the RBD.

              Specifies the name of the Ceph pool containing the RBD.

              Specifies the username (without the 'client.'  prefix)  used  to  access  the  Ceph

              Skip operations against known bad blocks.


       While running, fio will display the status of the created jobs.  For example:

              Threads: 1: [_r] [24.8% done] [ 13509/  8334 kb/s] [eta 00h:01m:31s]

       The  characters  in  the  first set of brackets denote the current status of each threads.
       The possible values are:

              P      Setup but not started.
              C      Thread created.
              I      Initialized, waiting.
              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.
              F      Running, currently waiting for fsync(2).
              V      Running, verifying written data.
              E      Exited, not reaped by main thread.
              -      Exited, thread reaped.

       The second set of brackets shows the estimated completion percentage of the current group.
       The  third set shows the read and write I/O rate, respectively. Finally, the estimated run
       time of the job is displayed.

       When fio completes (or is interrupted by Ctrl-C), it will show data for each thread,  each
       group of threads, and each disk, in that order.

       Per-thread statistics first show the threads client number, group-id, and error code.  The
       remaining figures are as follows:

              io     Number of megabytes of I/O performed.

              bw     Average data rate (bandwidth).

              runt   Threads run time.

              slat   Submission latency minimum, maximum, average and standard deviation. This is
                     the time it took to submit the I/O.

              clat   Completion  latency  minimum, maximum, average and standard deviation.  This
                     is the time between submission and completion.

              bw     Bandwidth minimum, maximum,  percentage  of  aggregate  bandwidth  received,
                     average and standard deviation.

              cpu    CPU  usage  statistics.  Includes  user  and  system time, number of context
                     switches this thread went through and number of major and minor page faults.

              IO depths
                     Distribution of I/O depths.  Each depth includes everything  less  than  (or
                     equal) to it, but greater than the previous depth.

              IO issued
                     Number  of  read/write  requests  issued,  and  number  of  short read/write

              IO latencies
                     Distribution of I/O completion  latencies.   The  numbers  follow  the  same
                     pattern as IO depths.

       The group statistics show:
              io     Number of megabytes I/O performed.
              aggrb  Aggregate bandwidth of threads in the group.
              minb   Minimum average bandwidth a thread saw.
              maxb   Maximum average bandwidth a thread saw.
              mint   Shortest runtime of threads in the group.
              maxt   Longest runtime of threads in the group.

       Finally, disk statistics are printed with reads first:
              ios    Number of I/Os performed by all groups.
              merge  Number of merges in the I/O scheduler.
              ticks  Number of ticks we kept the disk busy.
                     Total time spent in the disk queue.
              util   Disk utilization.

       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.


       If the --minimal / --append-terse options are given, the results will be  printed/appended
       in  a  semicolon-delimited  format  suitable  for  scripted  use.   A  job description (if
       provided) follows on a new line.  Note that the first number in the line  is  the  version
       number.  If  the output has to be changed for some reason, this number will be incremented
       by 1 to signify that change.  The fields are:

              terse version, fio version, jobname, groupid, error

              Read status:
                     Total I/O (KB), bandwidth (KB/s), IOPS, runtime (ms)

                     Submission latency:
                            min, max, mean, standard deviation
                     Completion latency:
                            min, max, mean, standard deviation
                     Completion latency percentiles (20 fields):
                            Xth percentile=usec
                     Total latency:
                            min, max, mean, standard deviation
                            min, max, aggregate percentage of total, mean, standard deviation

              Write status:
                     Total I/O (KB), bandwidth (KB/s), IOPS, runtime (ms)

                     Submission latency:
                            min, max, mean, standard deviation
                     Completion latency:
                            min, max, mean, standard deviation
                     Completion latency percentiles (20 fields):
                            Xth percentile=usec
                     Total latency:
                            min, max, mean, standard deviation
                            min, max, aggregate percentage of total, mean, standard deviation

              CPU usage:
                     user, system, context switches, major page faults, minor page faults

              IO depth distribution:
                     <=1, 2, 4, 8, 16, 32, >=64

              IO latency distribution:
                            <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
                            <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000

              Disk utilization (1 for each disk used):
                     name, read ios, write ios, read merges,  write  merges,  read  ticks,  write
                     ticks, read in-queue time, write in-queue time, disk utilization percentage

              Error Info (dependent on continue_on_error, default off):
                     total # errors, first error code

              text description (if provided in config - appears on newline)


       Normally  you  would  run  fio  as  a  stand-alone application on the machine where the IO
       workload should be generated. However, it is also possible to run the frontend and backend
       of  fio  separately. This makes it possible to have a fio server running on the machine(s)
       where the IO workload should be running, while controlling it from another machine.

       To start the server, you would do:

       fio --server=args

       on that machine, 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.

       When a server is running, you can connect to it from a client. The client is run with:

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

       where --local-args are arguments that are  local  to  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.  You can connect to multiple clients as well,
       to do that you could run:

       fio --client=server2 --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>

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

       In  order  to  enable fio --client runs utilizing 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  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:



       fio was written by Jens Axboe <>, now Jens Axboe <>.
       This man page was written by Aaron Carroll <> based on documentation
       by Jens Axboe.


       Report bugs to the fio mailing list <>.  See README.


       For further documentation see HOWTO and README.
       Sample jobfiles are available in the examples directory.