Provided by: fio_2.1.3-1_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  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.

              Limit run time to runtime seconds.

              Generate per-job latency logs.

              Generate per-job bandwidth logs.

              Print statistics in a 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.

              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. Multiple of these options can be given, adding
              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.

              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.  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. The suffix is not case sensitive. 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.

       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 ':' charcater.

   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

              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.

              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  the  time,  excluding  all

                            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.

                            Random reads.

                            Random writes.

                     rw, readwrite
                            Mixed sequential reads and writes.

                     randrw Mixed random reads and writes.

              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. Allow 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, the
              fio will sum the results and report them as "mixed" instead.

              Seed the random number generator in a predictable way  so  results  are  repeatable
              across runs.  Default: true.

              Fio  can  either  use  the  random generator supplied by the OS to generator random
              offsets, or it can use it's own internal generator (based on Tausworthe).   Default
              is  to  use  the  internal  generator, which is often of better quality and faster.
              Default: false.

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

                     none   Do not pre-allocate space.

                     posix  Pre-allocate via posix_fallocate().

                     keep   Pre-allocate via fallocate() 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 of posix_fadvise(2) to advise the kernel what I/O patterns  are  likely  to  be
              issued. Default: true.

              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).   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 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.

       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.

       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
              seperating 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.

              Initialise 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  zeroes.  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.

              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 open files (default).  sequential Do  each  file  in
                            the set sequentially.

              The  number  of  I/Os  to  issue  before  switching  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
                            adjacents 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 asycnronous 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  callt  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

              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 my 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.

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

              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 job. This option is useful if there are several jobs which are
              intended  to  operate on a file in parallel in 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.

              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.

              Use  sync_file_range()  for  every  val  number of write operations. Fio will track
              range of writes that have happened since the last sync_file_range() 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

              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  seperation.  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 seperation.

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

              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 this job running on spcified  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 argements:


              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.

              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 indiciates 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  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.

              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.  Allowed values

                     md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256 sha512 sha1
                            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   Write extra information about  each  I/O  (timestamp,  block  number,
                            etc.). The block number is verified. See verify_pattern as well.

                     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.

              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=meta.

              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.

       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.

              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.

              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_log_log for behaviour of given filename. For this option, the postfix is

              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.log" is used. Even if the
              filename is given, fio will still append the type of log.

              Same as write_bw_log, but writes IOPS. If no filename is given  with  this  option,
              the  default filename of "jobname_type.log" is used. Even if the filename is given,
              fio will still append the type of log.

              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.

              Disable  measurements  of  total  latency numbers. Useful only for cutting back the
              number of calls to gettimeofday, 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.

              If  the  job  is  a CPU cycle-eater, attempt to use the specified percentage of CPU

              If the job is a CPU cycle-eater, split the load into cycles of the  given  time  in

              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()  reducing  options  (disable_clat,  disable_slat,
              disable_bw)  plus  reduce  precision  of  the timeout somewhat to really shrink the
              gettimeofday() 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() 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() 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

              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.

              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. 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,  the
       must come after the ioengine that defines them is selected.

              Attempt to use the specified percentage of CPU cycles.

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

              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.

              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

                     udp    User datagram protocol

                     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.

              Normaly 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.

              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 immidietly inside defragment  event,  and  free  right  after

              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 option is given, the results will be  printed  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)>


       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.