fio(1) General Commands Manual fio(1)
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.
--timeout=timeout
Limit run time to timeout seconds.
--latency-log
Generate per-job latency logs.
--bandwidth-log
Generate per-job bandwidth logs.
--minimal
Print statistics in a 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.
--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.
--readonly
Enable read-only safety checks.
--eta=when
Specifies when real-time ETA estimate should be printed. when may be one of `always', `never' or `auto'.
--readonly
Turn on safety read-only checks, preventing any attempted write.
--section=sec
Only run section sec from job file. Multiple of these options can be given, adding 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.
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. The types used are:
str String: a sequence of alphanumeric characters.
int SI integer: a whole number, possibly containing a suffix denoting the base unit of the value. Accepted suffixes are `k', 'M', 'G',
'T', and 'P', denoting kilo (1024), mega (1024^2), giga (1024^3), tera (1024^4), and peta (1024^5) respectively. The suffix is not
case sensitive. If prefixed with '0x', the value is assumed to be base 16 (hexadecimal). A suffix may include a trailing 'b', for
instance 'kb' is identical to 'k'. You can specify a base 10 value by using 'KiB', 'MiB', 'GiB', etc. This is useful for disk drives
where values are often given in base 10 values. Specifying '30GiB' will get you 30*1000^3 bytes.
bool Boolean: a true or false value. `0' denotes false, `1' denotes true.
irange Integer range: a range of integers specified in the format lower:upper or lower-upper. lower and upper may contain a suffix as
described above. If an option allows two sets of ranges, they are separated with a `,' or `/' character. For example: `8-8k/8M-4G'.
float_list
List of floating numbers: A list of floating numbers, separated by a ':' charcater.
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 `./'.
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.
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 the 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.
The option may be post-fixed with a lock batch number. If set, then each thread/process may do that amount of IOs to the file before
giving up the lock. Since lock acquisition is expensive, batching the lock/unlocks will speed up IO.
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.
randread
Random reads.
randwrite
Random writes.
rw, readwrite
Mixed sequential reads and writes.
randrw Mixed random reads and writes.
For mixed I/O, the default split is 50/50. For certain types of io the result may still be skewed a bit, since the speed may be dif-
ferent. 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 off-
set.
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. Allow values are 1024 or 1000, with 1024 being the default.
randrepeat=bool
Seed the random number generator in a predictable way so results are repeatable across runs. Default: true.
use_os_rand=bool
Fio can either use the random generator supplied by the OS to generator random offsets, or it can use it's own internal generator
(based on Tausworthe). Default is to use the internal generator, which is often of better quality and faster. Default: false.
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().
keep Pre-allocate via fallocate() with FALLOC_FL_KEEP_SIZE set.
0 Backward-compatible alias for 'none'.
1 Backward-compatible alias for 'posix'.
May not be available on all supported platforms. 'keep' is only available on Linux. If using ZFS on Solaris this must be set to
'none' because ZFS doesn't support it. Default: 'posix'.
fadvise_hint=bool
Use of posix_fadvise(2) to advise the kernel what I/O patterns are likely to be issued. Default: true.
size=int
Total size of I/O for this job. fio will run until this many bytes have been transfered, unless limited by other options (runtime,
for instance). Unless nrfiles and filesize options are given, this amount will be divided between the available files for the job.
If not set, fio will use the full size of the given files or devices. If the the files do not exist, size must be given. It is also
possible to give size as a percentage between 1 and 100. If size=20% is given, fio will use 20% of the full size of the given files
or devices.
fill_device=bool, fill_fs=bool
Sets size to something really large and waits for ENOSPC (no space left on device) as the terminating condition. Only makes sense
with sequential write. For a read workload, the mount point will be filled first then IO started on the result. This option doesn't
make sense if operating on a raw device node, since the size of that is already known by the file system. Additionally, writing
beyond end-of-device will not return ENOSPC there.
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.
blocksize=int[,int], bs=int[,int]
Block size for I/O units. Default: 4k. Values for reads and writes can be specified separately in the format read,write, either of
which may be empty to leave that value at its default.
blocksize_range=irange[,irange], bsrange=irange[,irange]
Specify a range of I/O block sizes. The issued I/O unit will always be a multiple of the minimum size, unless blocksize_unaligned
is set. Applies to both reads and writes if only one range is given, but can be specified separately with a comma seperating the
values. Example: bsrange=1k-4k,2k-8k. Also (see blocksize).
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: bss-
plit=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 align-
ment.
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.
zero_buffers
Initialise 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 automati-
cally 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 zeroes. Note that this is per block size unit, for file/disk wide compression level that
matches this setting, you'll also want to set refill_buffers.
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.
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 open files (default). sequential Do each file in the set sequentially.
The number of I/Os to issue before switching a new file can be specified by appending `:int' to the service type.
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 adjacents IOs into a single submission.
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 pur-
poses.
net Transfer over the network. The protocol to be used can be defined with the protocol parameter. Depending on the pro-
tocol, 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 asycnronous 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'.
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 my impose OS restrictions causing the desired depth not
to be achieved. This may happen on Linux when using libaio and not setting direct=1, since buffered IO is not async on that OS.
Keep an eye on the IO depth distribution in the fio output to verify that the achieved depth is as expected. Default: 1.
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.
direct=bool
If true, use non-buffered I/O (usually O_DIRECT). Default: false.
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 job. This option is useful if there are several jobs which are intended to
operate on a file in parallel in disjoint segments, with even spacing between the starting points.
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.
sync_file_range=str:int
Use sync_file_range() for every val number of write operations. Fio will track range of writes that have happened since the last
sync_file_range() call. str can currently be one or more of:
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 job exits. 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.
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 with-
out 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 con-
tinue without a random block map. As coverage will not be as complete as with random maps, this option is disabled by default.
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
Number of blocks to issue before waiting thinktime microseconds. 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 seperation. 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 seperation.
ratecycle=int
Average bandwidth for rate and ratemin over this number of milliseconds. Default: 1000ms.
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.
startdelay=int
Delay start of job for the specified number of seconds.
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 per-
formance settle before logging results, thus minimizing the runtime required for stable results. Note that the ramp_time is consid-
ered 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 indiciates the memory alignment of the IO memory buffers. Note that the given alignment is applied to the first IO unit buffer,
if using iodepth the alignment of the following buffers are given by the bs used. In other words, if using a bs that is a multiple
of the page sized in the system, all buffers will be aligned to this value. If using a bs that is not page aligned, the alignment of
subsequent IO memory buffers is the sum of the iomem_align and bs used.
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.
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.
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. Allowed values are:
md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256 sha512 sha1
Store appropriate checksum in the header of each block. crc32c-intel is hardware accelerated SSE4.2 driven, falls back
to regular crc32c if not supported by the system.
meta Write extra information about each I/O (timestamp, block number, etc.). The block number is verified. See verify_pat-
tern as well.
null Pretend to verify. Used for testing internals.
This option can be used for repeated burn-in tests of a system to make sure that the written data is also correctly read back. If
the data direction given is a read or random read, fio will assume that it should verify a previously written file. If the data
direction includes any form of write, the verify will be of the newly written data.
verify_sort=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.
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 inter-
esting to fill with a known pattern for io verification purposes. Depending on the width of the pattern, fio will fill 1/2/3/4 bytes
of the buffer at the time(it can be either a decimal or a hex number). The verify_pattern if larger than a 32-bit quantity has to be
a hex number that starts with either "0x" or "0X". Use with verify=meta.
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 veri-
fied, if verify_backlog_batch is larger than verify_backlog, some blocks will be verified more than once.
stonewall , wait_for_previous
Wait for preceding jobs in the job file to exit before starting this one. stonewall implies new_group.
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.
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 inter-
spersed 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.
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 life-
time. The included fio_generate_plots script uses gnuplot to turn these text files into nice graphs. See write_log_log for behaviour
of given filename. For this option, the postfix is _bw.log.
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 "job-
name_type.log" is used. Even if the filename is given, fio will still append the type of log.
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.log" is used.
Even if the filename is given, fio will still append the type of log.
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.
disable_lat=bool
Disable measurements of total latency numbers. Useful only for cutting back the number of calls to gettimeofday, as that does impact
performance at really high IOPS rates. Note that to really get rid of a large amount of these calls, this option must be used with
disable_slat and disable_bw as well.
disable_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.
exec_prerun=str
Before running the job, execute the specified command with system(3).
exec_postrun=str
Same as exec_prerun, but the command is executed after the job completes.
ioscheduler=str
Attempt to switch the device hosting the file to the specified I/O scheduler.
cpuload=int
If the job is a CPU cycle-eater, attempt to use the specified percentage of CPU cycles.
cpuchunks=int
If the job is a CPU cycle-eater, split the load into cycles of the given time in milliseconds.
disk_util=bool
Generate disk utilization statistics if the platform supports it. Default: true.
gtod_reduce=bool
Enable all of the gettimeofday() reducing options (disable_clat, disable_slat, disable_bw) plus reduce precision of the timeout
somewhat to really shrink the gettimeofday() call count. With this option enabled, we only do about 0.4% of the gtod() calls we
would have done if all time keeping was enabled.
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() calls. With this option, you can set one CPU aside for doing nothing but logging current time
to a shared memory location. Then the other threads/processes that run IO workloads need only copy that segment, instead of entering
the kernel with a gettimeofday() call. The CPU set aside for doing these time calls will be excluded from other uses. Fio will manu-
ally clear it from the CPU mask of other jobs.
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 comple-
tion. 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.
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. Each number is a floating number in the range (0,100], and the
maximum length of the list is 20. Use ':' to separate the numbers. For example, --percentile_list=99.5:99.9 will cause fio to report
the values of completion latency below which 99.5% and 99.9% of the observed latencies fell, respectively.
Ioengine Parameters List
Some parameters are only valid when a specific ioengine is in use. These are used identically to normal parameters, with the caveat that
when used on the command line, the must come after the ioengine that defines them is selected.
(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.
(net,netsplice)port=int
The TCP or UDP port to bind to or connect to.
(net,netsplice)protocol=str, proto=str
The network protocol to use. Accepted values are:
tcp Transmission control protocol
udp Unreliable datagram protocol
unix UNIX domain socket
When the protocol is TCP or UDP, the port must also be given, as well as the hostname if the job is a TCP listener or UDP reader.
For unix sockets, the normal filename option should be used and the port is invalid.
(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.
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 option is given, the results will be printed in a semicolon-delimited format suitable for scripted use - a job description
(if provided) follows on a new line. Note that the first number in the line is the version number. If the output has to be changed for
some reason, this number will be incremented by 1 to signify that change. The fields are:
terse version, fio version, jobname, groupid, error
Read status:
Total I/O (KB), bandwidth (KB/s), IOPS, runtime (ms)
Submission latency:
min, max, mean, standard deviation
Completion latency:
min, max, mean, standard deviation
Completion latency percentiles (20 fields):
Xth percentile=usec
Total latency:
min, max, mean, standard deviation
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 pos-
sible 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/host-
name/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)>
AUTHORS
fio was written by Jens Axboe <jens.axboe@oracle.com>, now Jens Axboe <jaxboe@fusionio.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.
SEE ALSO
For further documentation see HOWTO and README.
Sample jobfiles are available in the examples directory.
User Manual September 2007 fio(1)