OnWorks favicon

fio - Online in the Cloud

Run fio in OnWorks free hosting provider over Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

This is the command fio that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator



fio - flexible I/O tester


fio [options] [jobfile]...


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


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

Write output to filename.

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

Limit run time to runtime seconds.

Generate per-job bandwidth logs.

Print statistics in a terse, semicolon-delimited format.

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

Display version information and exit.

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

--help Display usage information and exit.

Perform test and validation of internal CPU clock

Test the speed of the builtin checksumming functions. If no argument is given, all
of them are tested. Or a comma separated list can be passed, in which case the
given ones are tested.

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

List all commands defined by ioengine, or print help for command defined by

Convert jobfile to a set of command-line options.

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

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

Report full output status every `time` period passed.

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

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

Set the internal smalloc pool size to kb kilobytes.

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

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

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

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

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

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


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

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

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


Some parameters may take arguments of a specific type. Anywhere a numeric value is
required, an arithmetic expression may be used, provided it is surrounded by parentheses.
Supported operators are:

addition (+)

subtraction (-)

multiplication (*)

division (/)

modulus (%)

exponentiation (^)

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

str String: a sequence of alphanumeric characters.

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

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

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

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

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

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

Prefix filenames with this directory. Used to place files in a location other than
`./'. You can specify a number of directories by separating the names with a ':'
character. These directories will be assigned equally distributed to job clones
creates with numjobs as long as they are using generated filenames. If specific
filename(s) are set fio will use the first listed directory, and thereby matching
the filename semantic which generates a file each clone if not specified, but let
all clones use the same if set. See filename for considerations regarding escaping
certain characters on some platforms.

fio normally makes up a file name based on the job name, thread number, and file
number. If you want to share files between threads in a job or several jobs,
specify a filename for each of them to override the default. If the I/O engine is
file-based, you can specify a number of files by separating the names with a `:'
character. `-' is a reserved name, meaning stdin or stdout, depending on the
read/write direction set. On Windows, disk devices are accessed as \.PhysicalDrive0
for the first device, \.PhysicalDrive1 for the second etc. Note: Windows and
FreeBSD prevent write access to areas of the disk containing in-use data (e.g.
filesystems). If the wanted filename does need to include a colon, then escape that
with a '\' character. For instance, if the filename is "/dev/dsk/foo@3,0:c", then
you would use filename="/dev/dsk/foo@3,0\:c".

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

The name of the worker thread or process.

The incremental number of the worker thread or process.

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

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

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

none No locking. This is the default.

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

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

opendir=str Recursively open any files below directory str.

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

read Sequential reads.

write Sequential writes.

trim Sequential trim (Linux block devices only).

Random reads.

Random writes.

Random trim (Linux block devices only).

rw, readwrite
Mixed sequential reads and writes.

randrw Mixed random reads and writes.

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

For mixed I/O, the default split is 50/50. For certain types of io the result may
still be skewed a bit, since the speed may be different. It is possible to specify
a number of IO's to do before getting a new offset, this is done by appending a
`:<nr> to the end of the string given. For a random read, it would look like
rw=randread:8 for passing in an offset modifier with a value of 8. If the postfix
is used with a sequential IO pattern, then the value specified will be added to the
generated offset for each IO. For instance, using rw=write:4k will skip 4k for
every write. It turns sequential IO into sequential IO with holes. See the
rw_sequencer option.

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

Generate sequential offset

Generate the same offset

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

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

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

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

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

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

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

none Do not pre-allocate space.

posix Pre-allocate via posix_fallocate(3).

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

0 Backward-compatible alias for 'none'.

1 Backward-compatible alias for 'posix'.

May not be available on all supported platforms. 'keep' is only available on Linux.
If using ZFS on Solaris this must be set to 'none' because ZFS doesn't support it.
Default: 'posix'.

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

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

Total size of I/O for this job. fio will run until this many bytes have been
transferred, unless limited by other options (runtime, for instance, or
increased/descreased by io_size). Unless nrfiles and filesize options are given,
this amount will be divided between the available files for the job. If not set,
fio will use the full size of the given files or devices. If the files do not
exist, size must be given. It is also possible to give size as a percentage between
1 and 100. If size=20% is given, fio will use 20% of the full size of the given
files or devices.

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

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

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

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

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

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

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

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

blockalign=int[,int], ba=int[,int]
At what boundary to align random IO offsets. Defaults to the same as 'blocksize'
the minimum blocksize given. Minimum alignment is typically 512b for using direct
IO, though it usually depends on the hardware block size. This option is mutually
exclusive with using a random map for files, so it will turn off that option.

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

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

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

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

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

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

If set, fio will fill the IO buffers with this pattern. If not set, the contents of
IO buffers is defined by the other options related to buffer contents. The setting
can be any pattern of bytes, and can be prefixed with 0x for hex values. It may
also be a string, where the string must then be wrapped with "", e.g.:

Also you can combine everything together in any order:


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

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

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

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

random Choose a file at random.

Round robin over opened files (default).

Do each file in the set sequentially.

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

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

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

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

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

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

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

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

Solaris native asynchronous I/O.

Windows native asynchronous I/O.

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

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

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

sg SCSI generic sg v3 I/O. May be either synchronous using the SG_IO
ioctl, or if the target is an sg character device, we use read(2) and
write(2) for asynchronous I/O.

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

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

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

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

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

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

IO engine that does regular linux native fallocate call to
simulate data transfer as fio ioengine
DDIR_READ does fallocate(,mode = FALLOC_FL_KEEP_SIZE,)
DIR_WRITE does fallocate(,mode = 0)
DDIR_TRIM does fallocate(,mode =

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Make every Nth write a barrier write.

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




So if you do sync_file_range=wait_before,write:8, fio would use
the sync_file_range(2) man page. This option is Linux specific.

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

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

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

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

Percentage of a mixed workload that should be writes. If rwmixread and rwmixwrite
are given and do not sum to 100%, the latter of the two overrides the first. This
may interfere with a given rate setting, if fio is asked to limit reads or writes
to a certain rate. If that is the case, then the distribution may be skewed.
Default: 50.

By default, fio will use a completely uniform random distribution when asked to
perform random IO. Sometimes it is useful to skew the distribution in specific
ways, ensuring that some parts of the data is more hot than others. Fio includes
the following distribution models:

random Uniform random distribution

zipf Zipf distribution

pareto Pareto distribution

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

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

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

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

Fio supports the following engines for generating IO offsets for random IO:

Strong 2^88 cycle random number generator

lfsr Linear feedback shift register generator

Strong 64-bit 2^258 cycle random number generator

Tausworthe is a strong random number generator, but it requires tracking on
side if we want to ensure that blocks are only read or written once. LFSR
guarantees that we never generate the same offset twice, and it's also less
computationally expensive. It's not a true random generator, however, though for IO
purposes it's typically good enough. LFSR only works with single block sizes, not
with workloads that use multiple block sizes. If used with such a workload, fio may
read or write some blocks multiple times.

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

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

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

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

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

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

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

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

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

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

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

If set, fio will attempt to find the max performance point that the given workload
will run at while maintaining a latency below this target. The values is given in
microseconds. See latency_window and latency_percentile.

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

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

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

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

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

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

shared All jobs will share the CPU set specified.

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

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

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

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


mode is one of the following memory policy:

default, prefer, bind, interleave, local

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

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

Terminate processing after the specified number of seconds.

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

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

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

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

iomem=str, mem=str
Allocation method for I/O unit buffer. Allowed values are:

malloc Allocate memory with malloc(3).

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

Same as shm, but use huge pages as backing.

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

Same as mmap, but use huge files as backing.

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

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

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

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

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

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

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

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

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

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

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

If this isn't set, fio will abort jobs that are destructive (eg that write) to what
appears to be a mounted device or partition. This should help catch creating
inadvertently destructive tests, not realizing that the test will destroy data on
the mounted file system. Default: false.

If this is given, files will be pre-read into memory before starting the given IO
operation. This will also clear the invalidate flag, since it is pointless to pre-
read and then drop the cache. This will only work for IO engines that are seekable,
since they allow you to read the same data multiple times. Thus it will not work on
eg network or splice IO.

Unlink job files when done. Default: false.

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

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

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

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

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

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

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

null Pretend to verify. Used for testing internals.

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

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

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

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

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

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


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

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

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

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

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

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

Number of verify blocks to discard/trim.

Verify that trim/discarded blocks are returned as zeroes.

Trim after this number of blocks are written.

Trim this number of IO blocks.

Enable experimental verification.

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

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

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

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

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

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

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

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

Give size of an IO zone. See zoneskip.

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

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

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

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

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

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

Scale sector offsets down by this factor when replaying traces.

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

If given, write a bandwidth log of the jobs in this job file. Can be used to store
data of the bandwidth of the jobs in their lifetime. The included
fio_generate_plots script uses gnuplot to turn these text files into nice graphs.
See write_lat_log for behaviour of given filename. For this option, the postfix is
_bw.x.log, where x is the index of the job (1..N, where N is the number of jobs).
If per_job_logs is false, then the filename will not include the job index.

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

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

By default, fio will log an entry in the iops, latency, or bw log for every IO that
completes. When writing to the disk log, that can quickly grow to a very large
size. Setting this option makes fio average the each log entry over the specified
period of time, reducing the resolution of the log. Defaults to 0.

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

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

If set, and log_compression is also set, fio will store the log files in a
compressed format. They can be decompressed with fio, using the --inflate-log
command line parameter. The files will be stored with a .fz suffix.

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

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

Disable measurements of completion latency numbers. See disable_lat.

Disable measurements of submission latency numbers. See disable_lat.

Disable measurements of throughput/bandwidth numbers. See disable_lat.

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

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

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

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

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

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



cpu Internal CPU clock source

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

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

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

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

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

Select a specific builtin performance test.

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

# mount -t cgroup -o blkio none /cgroup

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

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

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

Set group ID, see uid.

Base unit for reporting. Allowed values are:

0 Use auto-detection (default).

8 Byte based.

1 Bit based.

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

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

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

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

Enable the reporting of percentiles of completion latencies.

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

Ioengine Parameters List
Some parameters are only valid when a specific ioengine is in use. These are used
identically to normal parameters, with the caveat that when used on the command line, they
must come after the ioengine.

Attempt to use the specified percentage of CPU cycles.

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

Detect when IO threads are done, then exit.

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

The host name or IP address to use for TCP or UDP based IO. If the job is a TCP
listener or UDP reader, the hostname is not used and must be omitted unless it is a
valid UDP multicast address.

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

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

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

Set TCP_NODELAY on TCP connections.

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

tcp Transmission control protocol

tcpv6 Transmission control protocol V6

udp User datagram protocol

udpv6 User datagram protocol V6

unix UNIX domain socket

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

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

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

Set the desired socket buffer size for the connection.

Set the TCP maximum segment size (TCP_MAXSEG).

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

Configure donor file block allocation strategy
0(default): Preallocate donor's file on init

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

Specifies the name of the RBD.

Specifies the name of the Ceph pool containing the RBD.

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

Skip operations against known bad blocks.


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

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

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

P Setup but not started.
C Thread created.
I Initialized, waiting.
R Running, doing sequential reads.
r Running, doing random reads.
W Running, doing sequential writes.
w Running, doing random writes.
M Running, doing mixed sequential reads/writes.
m Running, doing mixed random reads/writes.
F Running, currently waiting for fsync(2).
V Running, verifying written data.
E Exited, not reaped by main thread.
- Exited, thread reaped.

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

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

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

io Number of megabytes of I/O performed.

bw Average data rate (bandwidth).

runt Threads run time.

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

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

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

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

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

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

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

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

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

It is also possible to get fio to dump the current output while it is running, without
terminating the job. To do that, send fio the USR1 signal.


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

terse version, fio version, jobname, groupid, error

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

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

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

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

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

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

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

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

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

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


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

To start the server, you would do:

fio --server=args

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

1) fio --server

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

2) fio --server=ip:hostname,4444

Start a fio server, listening on IP belonging to hostname and on port 4444.

3) fio --server=ip6:::1,4444

Start a fio server, listening on IPv6 localhost ::1 and on port 4444.

4) fio --server=,4444

Start a fio server, listening on all interfaces on port 4444.

5) fio --server=

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

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

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

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

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

where --local-args are arguments that are local to the client where it is running,
'server' is the connect string, and --remote-args and <job file(s)> are sent to the
server. The 'server' string follows the same format as it does on the server side, to
allow IP/hostname/socket and port strings. You can connect to multiple clients as well,
to do that you could run:

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

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

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

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

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


The fio command would then be:

fio --client=host.list <job file>

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

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



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


Report bugs to the fio mailing list <[email protected]>. See README.

Use fio online using onworks.net services

Free Servers & Workstations

Download Windows & Linux apps

Linux commands

  • 1
    4ti2 - software package for algebraic,
    geometric and combinatorial problems on
    linear spaces ...
    Run 4ti2-qsolve
  • 2
    4ti2 - software package for algebraic,
    geometric and combinatorial problems on
    linear spaces ...
    Run 4ti2-rays
  • 3
    crashmail - A Fidonet *.JAM and MSG
    tosser ...
    Run crashmail
  • 4
    crashmaint - Do maintanence on
    CrashMail message bases ...
    Run crashmaint
  • 5
    GAP - Groups, Algorithms and
    Programming DESCRIPTION: GAP is a system
    for computational discrete algebra with
    particular emphasis on computational
    group theory...
    Run gap.real
  • 6
    GAP - Groups, Algorithms and
    Programming DESCRIPTION: GAP is a system
    for computational discrete algebra with
    particular emphasis on computational
    group theory...
    Run gap.sh
  • More »