Ubuntu Manpage: fio - flexible I/O tester

NAME

       fio - flexible I/O tester

SYNOPSIS

       fio [options] [jobfile]...

DESCRIPTION

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

OPTIONS

--debug=type
Enable verbose tracing 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.

--output=filename
Write output to filename.

--output-format=format
Set the reporting format to normal, terse, or json.

--runtime=runtime
Limit run time to runtime seconds.

--bandwidth-log
Generate per-job bandwidth logs.

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

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

--version
Display version information and exit.

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

--help Display usage information and exit.

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

--crctest[=test]
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.

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

--enghelp=ioengine[,command]
List all commands defined by ioengine, or print help for command defined by ioengine.

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

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

--eta-newline=time
Force an ETA newline for every `time` period passed.

--status-interval=time
Report full output status every `time` period passed.

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

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

--alloc-size=kb
Set the internal smalloc pool size to kb kilobytes.

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

--max-jobs=nr
Set the maximum allowed number of jobs (threads/processes) to support.

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

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

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

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

JOB FILE FORMAT

       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 sections.

JOB PARAMETERS

Types
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'.

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

Parameter List
name=str
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.

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

directory=str
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.

filename=str
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".

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

$jobname
The name of the worker thread or process.

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

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

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

lockfile=str
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.

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

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

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).

randread
Random reads.

randwrite
Random writes.

randtrim
Random trim (Linux block devices only).

rw, readwrite
Mixed sequential reads and writes.

randrw Mixed random reads and writes.

trimwrite
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.

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

sequential
Generate sequential offset

identical
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.

kb_base=int
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.

unified_rw_reporting=bool
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.

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

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

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

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

none Do not pre-allocate space.

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'.

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

fadvise_stream=int
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.

size=int
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.

filesize=irange
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.

file_append=bool
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).

bssplit=str
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.

bs_is_seq_rand=bool
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.

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

refill_buffers
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.

scramble_buffers=bool
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.

buffer_compress_percentage=int
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.

buffer_compress_chunk=int
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.

buffer_pattern=str
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.:
buffer_pattern="abcd"
or
buffer_pattern=-12
or
buffer_pattern=0xdeadface

Also you can combine everything together in any order:

buffer_pattern=0xdeadface"abcd"-12

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

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

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

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

random Choose a file at random.

roundrobin
Round robin over opened files (default).

sequential
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.

ioengine=str
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 location.

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 options.

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

solarisaio
Solaris native asynchronous I/O.

windowsaio
Windows native asynchronous I/O.

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.

syslet-rw
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.

netsplice
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 <http://www.xmailserver.org/guasi-lib.html>.

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.

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

falloc
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 = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE)

e4defrag
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.

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

libhdfs
Read and write through Hadoop (HDFS). The filename option is used to specify
host,port of the hdfs name-node to connect. This engine interprets offsets a little
differently. In HDFS, files once created cannot be modified. So random writes are
not possible. To imitate this, 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 properly.

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.

iodepth=int
Number of I/O units to keep in flight against the file. Note that increasing iodepth beyond 1 will
not affect synchronous ioengines (except for small 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.

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

iodepth_batch_complete=int
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 calls.

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

io_submit_mode=str
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).

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

atomic=bool
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.

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

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

offset_increment=int
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.

number_ios=int
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.

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

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

write_barrier=int
Make every Nth write a barrier write.

sync_file_range=str:int
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:

wait_before
SYNC_FILE_RANGE_WAIT_BEFORE

write SYNC_FILE_RANGE_WRITE

wait_after
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.

overwrite=bool
If writing, setup the file first and do overwrites. Default: false.

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

fsync_on_close=bool
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.

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

rwmixwrite=int
Percentage of a mixed workload that should be writes. If 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.

random_distribution=str:float
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.

percentage_random=int
For a random workload, set how big a percentage should be random. This defaults to 100%, in which
case the workload is fully random. It can be set from anywhere from 0 to 100. Setting it to 0
would make the workload fully sequential. It is possible to set different values for reads,
writes, and trim. To do so, simply use a comma separated list. See blocksize.

norandommap
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.

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

random_generator=str
Fio supports the following engines for generating IO offsets for random IO:

tausworthe
Strong 2^88 cycle random number generator

lfsr Linear feedback shift register generator

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

Tausworthe is a strong random number generator, but it requires tracking on the
side if we want to ensure that blocks are only read or written once. LFSR guarantees that we never
generate the same offset twice, and it's also less computationally expensive. It's not a true
random generator, however, though for 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.

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

prio=int
Set I/O priority value of this job between 0 (highest) and 7 (lowest). See ionice(1).

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

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

thinktime_spin=int
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.

thinktime_blocks=int
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.

rate=int
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.

ratemin=int
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.

rate_iops=int
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 metric.

rate_iops_min=int
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.

ratecycle=int
Average bandwidth for rate and ratemin over this number of milliseconds. Default: 1000ms.

latency_target=int
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.

latency_window=int
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.

latency_percentile=float
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.

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

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

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

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

shared All jobs will share the CPU set specified.

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

shared is the default 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.

numa_cpu_nodes=str
Set this job running on specified NUMA nodes' CPUs. The arguments allow comma delimited list of
cpu numbers, A-B ranges, or 'all'.

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

<mode>[:<nodelist>]

mode is one of the following memory 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'.

startdelay=irange
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.

runtime=int
Terminate processing after the specified number of seconds.

time_based
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 allows.

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

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

iomem=str, mem=str
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).

shmhuge
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'.

mmaphuge
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.

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

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

bwavgtime=int
Average bandwidth calculations over the given time in milliseconds. Default: 500ms.

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

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

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

create_on_open=bool
If true, the files are not created until they are opened for IO by the job.

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

allow_file_create=bool
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.

allow_mounted_write=bool
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.

pre_read=bool
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=bool
Unlink job files when done. Default: false.

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

verify_only=bool
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.

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

verify=str
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.

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

null 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.

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

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

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

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

verify_pattern=str
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.:
verify_pattern=%o
Or use combination of everything:

verify_pattern=0xff%o"abcd"-21

verify_fatal=bool
If true, exit the job on the first observed verification failure. Default: false.

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

verify_async=int
Fio will normally verify 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.

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

verify_backlog=int
Fio will normally verify the written contents of a job that utilizes verify once that job has
completed. In other words, everything is written then everything is read back and verified. You
may want to verify continually instead for a variety of reasons. Fio stores the meta data
associated with an 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.

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

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

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

trim_backlog=int
Trim after this number of blocks are written.

trim_backlog_batch=int
Trim this number of IO blocks.

experimental_verify=bool
Enable experimental verification.

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

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

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

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.

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

group_reporting
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 fork(2).

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

zonerange=int
Give size of an IO zone. See zoneskip.

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

write_iolog=str
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.

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

replay_no_stall=int
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.

replay_redirect=str
While replaying I/O patterns using read_iolog the default behavior is to replay the IOPS onto the
major/minor device that each IOP was recorded from. Setting replay_redirect causes all IOPS to be
replayed onto the single specified device regardless of the device it was recorded from.

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

replay_scale=int
Scale sector offsets down by this factor when replaying traces.

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

write_bw_log=str
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.

write_lat_log=str
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.

write_iops_log=str
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.

log_avg_msec=int
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.

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

log_compression=int
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.

log_store_compressed=bool
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.

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

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

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

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

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

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

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

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

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

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

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

gettimeofday
gettimeofday(2)

clock_gettime
clock_gettime(2)

cpu Internal CPU clock source

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

gtod_reduce=bool
Enable all of the gettimeofday(2) reducing options (disable_clat, disable_slat, disable_bw) 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.

gtod_cpu=int
Sometimes it's cheaper to dedicate a single thread of execution to just getting the current time.
Fio (and databases, for instance) are very intensive on gettimeofday(2) calls. With this option,
you can set one CPU aside for doing nothing but logging current time to a shared memory location.
Then the other threads/processes that run 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.

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

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

profile=str
Select a specific builtin performance test.

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

# mount -t cgroup -o blkio none /cgroup

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

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

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

gid=int
Set group ID, see uid.

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

0 Use auto-detection (default).

8 Byte based.

1 Bit based.

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

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

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

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

clat_percentiles=bool
Enable the reporting of percentiles of completion latencies.

percentile_list=float_list
Overwrite the default list of percentiles for completion latencies and the block error histogram.
Each number is a floating number in the range (0,100], and the maximum length of the list is 20.
Use ':' to separate the numbers. 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.

(cpu)cpuload=int
Attempt to use the specified percentage of CPU cycles.

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

(cpu)exit_on_io_done=bool
Detect when IO threads are done, then exit.

(libaio)userspace_reap
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).

(net,netsplice)hostname=str
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.

(net,netsplice)port=int
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.

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

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

(net,netsplice)nodelay=bool
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.

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

(net,pingpong)=bool
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.

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

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

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

(e4defrag,inplace)=int
Configure donor file block allocation strategy
0(default): Preallocate donor's file on init

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

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

(rbd)pool=str
Specifies the name of the Ceph pool containing the RBD.

(rbd)clientname=str
Specifies the username (without the 'client.' prefix) used to access the Ceph cluster.

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

OUTPUT

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 requests.

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.
io_queue
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.

TERSE OUTPUT

       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
                     Bandwidth:
                            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
                     Bandwidth:
                            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:
                     Microseconds:
                            <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
                     Milliseconds:
                            <=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)

CLIENT / SERVER

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=1.2.3.4

Start a fio server, listening on IP 1.2.3.4 on the default port.

6) fio --server=sock:/tmp/fio.sock

Start a fio server, listening on the local socket /tmp/fio.sock.

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:

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

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 192.168.10.120 and 192.168.10.121, then fio will create two files:

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

AUTHORS

       fio was written by Jens Axboe <jens.axboe@oracle.com>, now Jens Axboe <axboe@fb.com>.
       This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au> based on documentation by Jens Axboe.

REPORTING BUGS

       Report bugs to the fio mailing list <fio@vger.kernel.org>.  See README.