fio(1)fio(1)NAMEfio - flexible I/O tester
SYNOPSISfio [options] [jobfile]...
DESCRIPTIONfio is a tool that will spawn a number of threads or processes doing a
particular type of I/O action as specified by the user. The typical
use of fio is to write a job file matching the I/O load one wants to
simulate.
OPTIONS
--debug=type
Enable verbose tracing of various fio actions. May be `all' for
all types or individual types separated by a comma (eg
--debug=io,file). `help' will list all available tracing
options.
--output=filename
Write output to filename.
--output-format=format
Set the reporting format to normal, terse, json, or json+. Mul‐
tiple formats can be selected, separate by a comma. terse is a
CSV based format. json+ is like json, except it adds a full dump
of the latency buckets.
--runtime=runtime
Limit run time to runtime seconds.
--bandwidth-log
Generate per-job bandwidth logs.
--minimal
Print statistics in a terse, semicolon-delimited format.
--append-terse
Print statistics in selected mode AND terse, semicolon-delimited
format. Deprecated, use --output-format instead to select mul‐
tiple formats.
--version
Display version information and exit.
--terse-version=version
Set terse version output format (Current version 3, or older
version 2).
--help Display usage information and exit.
--cpuclock-test
Perform test and validation of internal CPU clock
--crctest[=test]
Test the speed of the builtin checksumming functions. If no
argument is given, all of them are tested. Or a comma separated
list can be passed, in which case the given ones are tested.
--cmdhelp=command
Print help information for command. May be `all' for all com‐
mands.
--enghelp=ioengine[,command]
List all commands defined by ioengine, or print help for command
defined by ioengine.
--showcmd=jobfile
Convert jobfile to a set of command-line options.
--eta=when
Specifies when real-time ETA estimate should be printed. when
may be one of `always', `never' or `auto'.
--eta-newline=time
Force an ETA newline for every `time` period passed.
--status-interval=time
Report full output status every `time` period passed.
--readonly
Turn on safety read-only checks, preventing any attempted write.
--section=sec
Only run section sec from job file. This option can be used mul‐
tiple times to add more sections to run.
--alloc-size=kb
Set the internal smalloc pool size to kb kilobytes.
--warnings-fatal
All fio parser warnings are fatal, causing fio to exit with an
error.
--max-jobs=nr
Set the maximum allowed number of jobs (threads/processes) to
support.
--server=args
Start a backend server, with args specifying what to listen to.
See client/server section.
--daemonize=pidfile
Background a fio server, writing the pid to the given pid file.
--client=host
Instead of running the jobs locally, send and run them on the
given host or set of hosts. See client/server section.
--idle-prof=option
Report cpu idleness on a system or percpu basis (option=sys‐
tem,percpu) or run unit work calibration only (option=cali‐
brate).
JOB FILE FORMAT
Job files are in `ini' format. They consist of one or more job defini‐
tions, 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 defi‐
nitions may override any parameter set in global sections.
JOB PARAMETERS
Types
Some parameters may take arguments of a specific type. Anywhere a
numeric value is required, an arithmetic expression may be used, pro‐
vided 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 denot‐
ing 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 pre‐
fixed with '0x', the value is assumed to be base 16 (hexadeci‐
mal). 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 sec‐
onds. The suffixes are not case sensitive.
bool Boolean: a true or false value. `0' denotes false, `1' denotes
true.
irange Integer range: a range of integers specified in the format
lower:upper or lower-upper. lower and upper may contain a suffix
as described above. If an option allows two sets of ranges,
they are separated with a `,' or `/' character. For example:
`8-8k/8M-4G'.
float_list
List of floating numbers: A list of floating numbers, separated
by a ':' character.
Parameter List
name=str
May be used to override the job name. On the command line, this
parameter has the special purpose of signalling the start of a
new job.
wait_for=str
Specifies the name of the already defined job to wait for. Sin‐
gle waitee name only may be specified. If set, the job won't be
started until all workers of the waitee job are done. Wait_for
operates on the job name basis, so there are a few limitations.
First, the waitee must be defined prior to the waiter job (mean‐
ing no forward references). Second, if a job is being referenced
as a waitee, it must have a unique name (no duplicate waitees).
description=str
Human-readable description of the job. It is printed when the
job is run, but otherwise has no special purpose.
directory=str
Prefix filenames with this directory. Used to place files in a
location other than `./'. You can specify a number of directo‐
ries by separating the names with a ':' character. These direc‐
tories will be assigned equally distributed to job clones cre‐
ates with numjobs as long as they are using generated filenames.
If specific filename(s) are set fio will use the first listed
directory, and thereby matching the filename semantic which
generates a file each clone if not specified, but let all clones
use the same if set. See filename for considerations regarding
escaping certain characters on some platforms.
filename=str
fio normally makes up a file name based on the job name, thread
number, and file number. If you want to share files between
threads in a job or several jobs, specify a filename for each of
them to override the default. If the I/O engine is file-based,
you can specify a number of files by separating the names with a
`:' character. `-' is a reserved name, meaning stdin or stdout,
depending on the read/write direction set. On Windows, disk
devices are accessed as \.PhysicalDrive0 for the first device,
\.PhysicalDrive1 for the second etc. Note: Windows and FreeBSD
prevent write access to areas of the disk containing in-use data
(e.g. filesystems). If the wanted filename does need to include
a colon, then escape that with a '\' character. For instance, if
the filename is "/dev/dsk/foo@3,0:c", then you would use file‐
name="/dev/dsk/foo@3,0\:c".
filename_format=str
If sharing multiple files between jobs, it is usually necessary
to have fio generate the exact names that you want. By default,
fio will name a file based on the default file format specifica‐
tion of jobname.jobnumber.filenumber. With this option, that can
be customized. Fio will recognize and replace the following key‐
words in this string:
$jobname
The name of the worker thread or process.
$jobnum
The incremental number of the worker thread or
process.
$filenum
The incremental number of the file for that worker
thread or process.
To have dependent jobs share a set of files, this option can be
set to have fio generate filenames that are shared between the
two. For instance, if testfiles.$filenum is specified, file num‐
ber 4 for any job will be named testfiles.4. The default of
$jobname.$jobnum.$filenum will be used if no other format speci‐
fier is given.
lockfile=str
Fio defaults to not locking any files before it does IO to them.
If a file or file descriptor is shared, fio can serialize IO to
that file to make the end result consistent. This is usual for
emulating real workloads that share files. The lock modes are:
none No locking. This is the default.
exclusive
Only one thread or process may do IO at a time,
excluding all others.
readwrite
Read-write locking on the file. Many readers may
access the file at the same time, but writes get
exclusive access.
opendir=str Recursively open any files below directory str.
readwrite=str, rw=str
Type of I/O pattern. Accepted values are:
read Sequential reads.
write Sequential writes.
trim Sequential trim (Linux block devices only).
randread
Random reads.
randwrite
Random writes.
randtrim
Random trim (Linux block devices only).
rw, readwrite
Mixed sequential reads and writes.
randrw Mixed random reads and writes.
trimwrite
Trim and write mixed workload. Blocks will be
trimmed first, then the same blocks will be writ‐
ten to.
For mixed I/O, the default split is 50/50. For certain types of
io the result may still be skewed a bit, since the speed may be
different. It is possible to specify a number of IO's to do
before getting a new offset, this is done by appending a `:<nr>
to the end of the string given. For a random read, it would look
like rw=randread:8 for passing in an offset modifier with a
value of 8. If the postfix is used with a sequential IO pattern,
then the value specified will be added to the generated offset
for each IO. For instance, using rw=write:4k will skip 4k for
every write. It turns sequential IO into sequential IO with
holes. See the rw_sequencer option.
rw_sequencer=str
If an offset modifier is given by appending a number to the
rw=<str> line, then this option controls how that number modi‐
fies 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 nor‐
mally 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 sequen‐
tial IO is already sequential, setting sequential for that would
not result in any differences. identical behaves in a similar
fashion, except it sends the same offset 8 number of times
before generating a new offset.
kb_base=int
The base unit for a kilobyte. The defacto base is 2^10, 1024.
Storage manufacturers like to use 10^3 or 1000 as a base ten
unit instead, for obvious reasons. Allowed values are 1024 or
1000, with 1024 being the default.
unified_rw_reporting=bool
Fio normally reports statistics on a per data direction basis,
meaning that read, write, and trim are accounted and reported
separately. If this option is set fio sums the results and
reports them as "mixed" instead.
randrepeat=bool
Seed the random number generator used for random I/O patterns in
a predictable way so the pattern is repeatable across runs.
Default: true.
allrandrepeat=bool
Seed all random number generators in a predictable way so
results are repeatable across runs. Default: false.
randseed=int
Seed the random number generators based on this seed value, to
be able to control what sequence of output is being generated.
If not set, the random sequence depends on the randrepeat set‐
ting.
fallocate=str
Whether pre-allocation is performed when laying down files.
Accepted values are:
none Do not pre-allocate space.
posix Pre-allocate via posix_fallocate(3).
keep Pre-allocate via fallocate(2) with FAL‐
LOC_FL_KEEP_SIZE set.
0 Backward-compatible alias for 'none'.
1 Backward-compatible alias for 'posix'.
May not be available on all supported platforms. 'keep' is only
available on Linux. If using ZFS on Solaris this must be set to
'none' because ZFS doesn't support it. Default: 'posix'.
fadvise_hint=bool
Use posix_fadvise(2) to advise the kernel what I/O patterns are
likely to be issued. Default: true.
fadvise_stream=int
Use posix_fadvise(2) to advise the kernel what stream ID the
writes issued belong to. Only supported on Linux. Note, this
option may change going forward.
size=int
Total size of I/O for this job. fio will run until this many
bytes have been transferred, unless limited by other options
(runtime, for instance, or increased/descreased by io_size).
Unless nrfiles and filesize options are given, this amount will
be divided between the available files for the job. If not set,
fio will use the full size of the given files or devices. If the
files do not exist, size must be given. It is also possible to
give size as a percentage between 1 and 100. If size=20% is
given, fio will use 20% of the full size of the given files or
devices.
io_size=int, io_limit =int
Normally fio operates within the region set by size, which means
that the size option sets both the region and size of IO to be
performed. Sometimes that is not what you want. With this
option, it is possible to define just the amount of IO that fio
should do. For instance, if size is set to 20G and io_limit is
set to 5G, fio will perform IO within the first 20G but exit
when 5G have been done. The opposite is also possible - if size
is set to 20G, and io_size is set to 40G, then fio will do 40G
of IO within the 0..20G region.
fill_device=bool, fill_fs=bool
Sets size to something really large and waits for ENOSPC (no
space left on device) as the terminating condition. Only makes
sense with sequential write. For a read workload, the mount
point will be filled first then IO started on the result. This
option doesn't make sense if operating on a raw device node,
since the size of that is already known by the file system.
Additionally, writing beyond end-of-device will not return
ENOSPC there.
filesize=irange
Individual file sizes. May be a range, in which case fio will
select sizes for files at random within the given range, limited
to size in total (if that is given). If filesize is not speci‐
fied, each created file is the same size.
file_append=bool
Perform IO after the end of the file. Normally fio will operate
within the size of a file. If this option is set, then fio will
append to the file instead. This has identical behavior to set‐
ting 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 block‐
size_unaligned is set. Applies to both reads and writes if only
one range is given, but can be specified separately with a comma
separating the values. Example: bsrange=1k-4k,2k-8k. Also (see
blocksize).
bssplit=str
This option allows even finer grained control of the block sizes
issued, not just even splits between them. With this option, you
can weight various block sizes for exact control of the issued
IO for a job that has mixed block sizes. The format of the
option is bssplit=blocksize/percentage, optionally adding as
many definitions as needed separated by a colon. Example: 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
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 align‐
ment is typically 512b for using direct IO, though it usually
depends on the hardware block size. This option is mutually
exclusive with using a random map for files, so it will turn off
that option.
bs_is_seq_rand=bool
If this option is set, fio will use the normal read,write block‐
size settings as sequential,random instead. Any random read or
write will use the WRITE blocksize settings, and any sequential
read or write will use the READ blocksize setting.
zero_buffers
Initialize buffers with all zeros. Default: fill buffers with
random data.
refill_buffers
If this option is given, fio will refill the IO buffers on every
submit. The default is to only fill it at init time and reuse
that data. Only makes sense if zero_buffers isn't specified,
naturally. If data verification is enabled, refill_buffers is
also automatically enabled.
scramble_buffers=bool
If refill_buffers is too costly and the target is using data
deduplication, then setting this option will slightly modify the
IO buffer contents to defeat normal de-dupe attempts. This is
not enough to defeat more clever block compression attempts, but
it will stop naive dedupe of blocks. Default: true.
buffer_compress_percentage=int
If this is set, then fio will attempt to provide IO buffer con‐
tent (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 buf‐
fer_pattern. If the pattern option is used, it might skew the
compression ratio slightly. Note that this is per block size
unit, for file/disk wide compression level that matches this
setting. Note that this is per block size unit, for file/disk
wide compression level that matches this setting, you'll also
want to set refill_buffers.
buffer_compress_chunk=int
See buffer_compress_percentage. This setting allows fio to man‐
age how big the ranges of random data and zeroed data is. With‐
out this set, fio will provide buffer_compress_percentage of
blocksize random data, followed by the remaining zeroed. With
this set to some chunk size smaller than the block size, fio can
alternate random and zeroed data throughout the IO buffer.
buffer_pattern=str
If set, fio will fill the IO buffers with this pattern. If not
set, the contents of IO buffers is defined by the other options
related to buffer contents. The setting can be any pattern of
bytes, and can be prefixed with 0x for hex values. It may also
be a string, where the string must then be wrapped with "",
e.g.:
buffer_pattern="abcd"
or
buffer_pattern=-12
or
buffer_pattern=0xdeadface
Also you can combine everything together in any order:
buffer_pattern=0xdeadface"abcd"-12
dedupe_percentage=int
If set, fio will generate this percentage of identical buffers
when writing. These buffers will be naturally dedupable. The
contents of the buffers depend on what other buffer compression
settings have been set. It's possible to have the individual
buffers either fully compressible, or not at all. This option
only controls the distribution of unique buffers.
nrfiles=int
Number of files to use for this job. Default: 1.
openfiles=int
Number of files to keep open at the same time. Default:
nrfiles.
file_service_type=str
Defines how files to service are selected. The following types
are defined:
random Choose a file at random.
roundrobin
Round robin over opened files (default).
sequential
Do each file in the set sequentially.
The number of I/Os to issue before switching to a new file can
be specified by appending `:int' to the service type.
ioengine=str
Defines how the job issues I/O. The following types are
defined:
sync Basic read(2) or write(2) I/O. fseek(2) is used
to position the I/O location.
psync Basic pread(2) or pwrite(2) I/O.
vsync Basic readv(2) or writev(2) I/O. Will emulate
queuing by coalescing adjacent IOs into a single
submission.
pvsync Basic preadv(2) or pwritev(2) I/O.
libaio Linux native asynchronous I/O. This ioengine
defines engine specific options.
posixaio
POSIX asynchronous I/O using aio_read(3) and
aio_write(3).
solarisaio
Solaris native asynchronous I/O.
windowsaio
Windows native asynchronous I/O.
mmap File is memory mapped with mmap(2) and data copied
using memcpy(3).
splice splice(2) is used to transfer the data and
vmsplice(2) to transfer data from user-space to
the kernel.
syslet-rw
Use the syslet system calls to make regular
read/write asynchronous.
sg SCSI generic sg v3 I/O. May be either synchronous
using the SG_IO ioctl, or if the target is an sg
character device, we use read(2) and write(2) for
asynchronous I/O.
null Doesn't transfer any data, just pretends to.
Mainly used to exercise fio itself and for debug‐
ging and testing purposes.
net Transfer over the network. The protocol to be
used can be defined with the protocol parameter.
Depending on the protocol, filename, hostname,
port, or listen must be specified. This ioengine
defines engine specific options.
netsplice
Like net, but uses splice(2) and vmsplice(2) to
map data and send/receive. This ioengine defines
engine specific options.
cpuio Doesn't transfer any data, but burns CPU cycles
according to cpuload and cpucycles parameters.
guasi The GUASI I/O engine is the Generic Userspace
Asynchronous Syscall Interface approach to asyn‐
chronous I/O.
See <http://www.xmailserver.org/guasi-lib.html>.
rdma The RDMA I/O engine supports both RDMA memory
semantics (RDMA_WRITE/RDMA_READ) and channel
semantics (Send/Recv) for the InfiniBand, RoCE and
iWARP protocols.
external
Loads an external I/O engine object file. Append
the engine filename as `:enginepath'.
falloc
IO engine that does regular linux native fallo‐
cate call to simulate data transfer as fio
ioengine
DDIR_READ does fallocate(,mode = FAL‐
LOC_FL_KEEP_SIZE,)
DIR_WRITE does fallocate(,mode = 0)
DDIR_TRIM does fallocate(,mode = FAL‐
LOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE)
e4defrag
IO engine that does regular EXT4_IOC_MOVE_EXT
ioctls to simulate defragment activity request to
DDIR_WRITE event
rbd IO engine supporting direct access to Ceph Rados
Block Devices (RBD) via librbd without the need to
use the kernel rbd driver. This ioengine defines
engine specific options.
gfapi Using Glusterfs libgfapi sync interface to direct
access to Glusterfs volumes without having to go
through FUSE. This ioengine defines engine spe‐
cific options.
gfapi_async
Using Glusterfs libgfapi async interface to direct
access to Glusterfs volumes without having to go
through FUSE. This ioengine defines engine spe‐
cific options.
libhdfs
Read and write through Hadoop (HDFS). The file‐
name option is used to specify host,port of the
hdfs name-node to connect. This engine interprets
offsets a little differently. In HDFS, files once
created cannot be modified. So random writes are
not possible. To imitate this, libhdfs engine
expects bunch of small files to be created over
HDFS, and engine will randomly pick a file out of
those files based on the offset generated by fio
backend. (see the example job file to create such
files, use rw=write option). Please note, you
might want to set necessary environment variables
to work with hdfs/libhdfs properly.
mtd Read, write and erase an MTD character device
(e.g., /dev/mtd0). Discards are treated as erases.
Depending on the underlying device type, the I/O
may have to go in a certain pattern, e.g., on
NAND, writing sequentially to erase blocks and
discarding before overwriting. The writetrim mode
works well for this constraint.
iodepth=int
Number of I/O units to keep in flight against the file. Note
that increasing iodepth beyond 1 will not affect synchronous
ioengines (except for small degress when verify_async is in
use). Even async engines may impose OS restrictions causing the
desired depth not to be achieved. This may happen on Linux when
using libaio and not setting direct=1, since buffered IO is not
async on that OS. Keep an eye on the IO depth distribution in
the fio output to verify that the achieved depth is as expected.
Default: 1.
iodepth_batch=int, iodepth_batch_submit=int
This defines how many pieces of IO to submit at once. It
defaults to 1 which means that we submit each IO as soon as it
is available, but can be raised to submit bigger batches of IO
at the time. If it is set to 0 the iodepth value will be used.
iodepth_batch_complete_min=int, 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_batch_complete_max=int
This defines maximum pieces of IO to retrieve at once. This
variable should be used along with iodepth_batch_com‐
plete_min=int variable, specifying the range of min and max
amount of IO which should be retrieved. By default it is equal
to iodepth_batch_complete_min value.
Example #1:
iodepth_batch_complete_min=1
iodepth_batch_complete_max=<iodepth>
which means that we will retrieve at leat 1 IO and up to the
whole submitted queue depth. If none of IO has been completed
yet, we will wait.
Example #2:
iodepth_batch_complete_min=0
iodepth_batch_complete_max=<iodepth>
which means that we can retrieve up to the whole submitted queue
depth, but if none of IO has been completed yet, we will NOT
wait and immediately exit the system call. In this example we
simply do polling.
iodepth_low=int
Low watermark indicating when to start filling the queue again.
Default: iodepth.
io_submit_mode=str
This option controls how fio submits the IO to the IO engine.
The default is inline, which means that the fio job threads sub‐
mit 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 submis‐
sion rates independently of the device completion rates. This
avoids skewed latency reporting if IO gets back up on the device
side (the coordinated omission problem).
direct=bool
If true, use non-buffered I/O (usually O_DIRECT). Default:
false.
atomic=bool
If value is true, attempt to use atomic direct IO. Atomic writes
are guaranteed to be stable once acknowledged by the operating
system. Only Linux supports O_ATOMIC right now.
buffered=bool
If true, use buffered I/O. This is the opposite of the direct
parameter. Default: true.
offset=int
Offset in the file to start I/O. Data before the offset will not
be touched.
offset_increment=int
If this is provided, then the real offset becomes the offset +
offset_increment * thread_number, where the thread number is a
counter that starts at 0 and is incremented for each sub-job
(i.e. when numjobs option is specified). This option is useful
if there are several jobs which are intended to operate on a
file in parallel disjoint segments, with even spacing between
the starting points.
number_ios=int
Fio will normally perform IOs until it has exhausted the size of
the region set by size, or if it exhaust the allocated time (or
hits an error condition). With this setting, the range/size can
be set independently of the number of IOs to perform. When fio
reaches this number, it will exit normally and report status.
Note that this does not extend the amount of IO that will be
done, it will only stop fio if this condition is met before
other end-of-job criteria.
fsync=int
How many I/Os to perform before issuing an fsync(2) of dirty
data. If 0, don't sync. Default: 0.
fdatasync=int
Like fsync, but uses fdatasync(2) instead to only sync the data
parts of the file. Default: 0.
write_barrier=int
Make every Nth write a barrier write.
sync_file_range=str:int
Use sync_file_range(2) for every val number of write operations.
Fio will track range of writes that have happened since the last
sync_file_range(2) call. str can currently be one or more of:
wait_before
SYNC_FILE_RANGE_WAIT_BEFORE
write SYNC_FILE_RANGE_WRITE
wait_after
SYNC_FILE_RANGE_WRITE
So if you do sync_file_range=wait_before,write:8, fio
would use
SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for every 8
writes. Also see the sync_file_range(2) man page. This option
is Linux specific.
overwrite=bool
If writing, setup the file first and do overwrites. Default:
false.
end_fsync=bool
Sync file contents when a write stage has completed. Default:
false.
fsync_on_close=bool
If true, sync file contents on close. This differs from
end_fsync in that it will happen on every close, not just at the
end of the job. Default: false.
rwmixread=int
Percentage of a mixed workload that should be reads. Default:
50.
rwmixwrite=int
Percentage of a mixed workload that should be writes. If
rwmixread and rwmixwrite are given and do not sum to 100%, the
latter of the two overrides the first. This may interfere with a
given rate setting, if fio is asked to limit reads or writes to
a certain rate. If that is the case, then the distribution may
be skewed. Default: 50.
random_distribution=str:float
By default, fio will use a completely uniform random distribu‐
tion 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, gen‐
zipf, that can be used visualize what the given input values
will yield in terms of hit rates. If you wanted to use zipf
with a theta of 1.2, you would use random_distribution=zipf:1.2
as the option. If a non-uniform model is used, fio will disable
use of the random map.
percentage_random=int
For a random workload, set how big a percentage should be ran‐
dom. 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, sim‐
ply use a comma separated list. See blocksize.
norandommap
Normally fio will cover every block of the file when doing ran‐
dom I/O. If this parameter is given, a new offset will be chosen
without looking at past I/O history. This parameter is mutually
exclusive with verify.
softrandommap=bool
See norandommap. If fio runs with the random block map enabled
and it fails to allocate the map, if this option is set it will
continue without a random block map. As coverage will not be as
complete as with random maps, this option is disabled by
default.
random_generator=str
Fio supports the following engines for generating IO offsets for
random IO:
tausworthe
Strong 2^88 cycle random number generator
lfsr Linear feedback shift register generator
tausworthe64
Strong 64-bit 2^258 cycle random number generator
Tausworthe is a strong random number generator, but it
requires tracking on the
side if we want to ensure that blocks are only read or written
once. LFSR guarantees that we never generate the same offset
twice, and it's also less computationally expensive. It's not a
true random generator, however, though for IO purposes it's typ‐
ically good enough. LFSR only works with single block sizes, not
with workloads that use multiple block sizes. If used with such
a workload, fio may read or write some blocks multiple times.
nice=int
Run job with given nice value. See nice(2).
prio=int
Set I/O priority value of this job between 0 (highest) and 7
(lowest). See ionice(1).
prioclass=int
Set I/O priority class. See ionice(1).
thinktime=int
Stall job for given number of microseconds between issuing I/Os.
thinktime_spin=int
Pretend to spend CPU time for given number of microseconds,
sleeping the rest of the time specified by thinktime. Only
valid if thinktime is set.
thinktime_blocks=int
Only valid if thinktime is set - control how many blocks to
issue, before waiting thinktime microseconds. If not set,
defaults to 1 which will make fio wait thinktime microseconds
after every block. This effectively makes any queue depth set‐
ting redundant, since no more than 1 IO will be queued before we
have to complete it and do our thinktime. In other words, this
setting effectively caps the queue depth if the latter is
larger. Default: 1.
rate=int
Cap bandwidth used by this job. The number is in bytes/sec, the
normal postfix rules apply. You can use rate=500k to limit reads
and writes to 500k each, or you can specify read and writes sep‐
arately. 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.
rate_min=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 sepa‐
ration.
rate_iops=int
Cap the bandwidth to this number of IOPS. Basically the same as
rate, just specified independently of bandwidth. The same format
as rate is used for read vs write separation. If blocksize is a
range, the smallest block size is used as the metric.
rate_iops_min=int
If this rate of I/O is not met, the job will exit. The same for‐
mat as rate is used for read vs write separation.
rate_process=str
This option controls how fio manages rated IO submissions. The
default is linear, which submits IO in a linear fashion with
fixed delays between IOs that gets adjusted based on IO comple‐
tion rates. If this is set to poisson, fio will submit IO based
on a more real world random request flow, known as the Poisson
process (https://en.wikipedia.org/wiki/Poisson_process). The
lambda will be 10^6 / IOPS for the given workload.
rate_cycle=int
Average bandwidth for rate and rate_min over this number of mil‐
liseconds. Default: 1000ms.
latency_target=int
If set, fio will attempt to find the max performance point that
the given workload will run at while maintaining a latency below
this target. The values is given in microseconds. See
latency_window and latency_percentile.
latency_window=int
Used with latency_target to specify the sample window that the
job is run at varying queue depths to test the performance. The
value is given in microseconds.
latency_percentile=float
The percentage of IOs that must fall within the criteria speci‐
fied by latency_target and latency_window. If not set, this
defaults to 100.0, meaning that all IOs must be equal or below
to the value set by latency_target.
max_latency=int
If set, fio will exit the job if it exceeds this maximum
latency. It will exit with an ETIME error.
cpumask=int
Set CPU affinity for this job. int is a bitmask of allowed CPUs
the job may run on. See sched_setaffinity(2).
cpus_allowed=str
Same as cpumask, but allows a comma-delimited list of CPU num‐
bers.
cpus_allowed_policy=str
Set the policy of how fio distributes the CPUs specified by
cpus_allowed or cpumask. Two policies are supported:
shared All jobs will share the CPU set specified.
split Each job will get a unique CPU from the CPU set.
shared is the default behaviour, if the option isn't specified.
If split is specified, then fio will assign one cpu per job. If
not enough CPUs are given for the jobs listed, then fio will
roundrobin the CPUs in the set.
numa_cpu_nodes=str
Set this job running on specified NUMA nodes' CPUs. The argu‐
ments allow comma delimited list of cpu numbers, A-B ranges, or
'all'.
numa_mem_policy=str
Set this job's memory policy and corresponding NUMA nodes. For‐
mat of the arguments:
<mode>[:<nodelist>]
mode is one of the following memory policy:
default, prefer, bind, interleave, local
For default and local memory policy, no nodelist is
needed to be specified. For prefer, only one node is allowed.
For bind and interleave, nodelist allows comma delimited list of
numbers, A-B ranges, or 'all'.
startdelay=irange
Delay start of job for the specified number of seconds. Supports
all time suffixes to allow specification of hours, minutes, sec‐
onds and milliseconds - seconds are the default if a unit is
omitted. Can be given as a range which causes each thread to
choose randomly out of the range.
runtime=int
Terminate processing after the specified number of seconds.
time_based
If given, run for the specified runtime duration even if the
files are completely read or written. The same workload will be
repeated as many times as runtime allows.
ramp_time=int
If set, fio will run the specified workload for this amount of
time before logging any performance numbers. Useful for letting
performance settle before logging results, thus minimizing the
runtime required for stable results. Note that the ramp_time is
considered lead in time for a job, thus it will increase the
total runtime if a special timeout or runtime is specified.
invalidate=bool
Invalidate buffer-cache for the file prior to starting I/O.
Default: true.
sync=bool
Use synchronous I/O for buffered writes. For the majority of
I/O engines, this means using O_SYNC. Default: false.
iomem=str, mem=str
Allocation method for I/O unit buffer. Allowed values are:
malloc Allocate memory with malloc(3).
shm Use shared memory buffers allocated through
shmget(2).
shmhuge
Same as shm, but use huge pages as backing.
mmap Use mmap(2) for allocation. Uses anonymous memory
unless a filename is given after the option in the
format `:file'.
mmaphuge
Same as mmap, but use huge files as backing.
mmapshared
Same as mmap, but use a MMAP_SHARED mapping.
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. Nor‐
mally you just need to echo an appropriate number, eg echoing 8
will ensure that the OS has 8 huge pages ready for use.
iomem_align=int, mem_align=int
This indicates the memory alignment of the IO memory buffers.
Note that the given alignment is applied to the first IO unit
buffer, if using iodepth the alignment of the following buffers
are given by the bs used. In other words, if using a bs that is
a multiple of the page sized in the system, all buffers will be
aligned to this value. If using a bs that is not page aligned,
the alignment of subsequent IO memory buffers is the sum of the
iomem_align and bs used.
hugepage-size=int
Defines the size of a huge page. Must be at least equal to the
system setting. Should be a multiple of 1MB. Default: 4MB.
exitall
Terminate all jobs when one finishes. Default: wait for each
job to finish.
exitall_on_error =bool
Terminate all jobs if one job finishes in error. Default: wait
for each job to finish.
bwavgtime=int
Average bandwidth calculations over the given time in millisec‐
onds. Default: 500ms.
iopsavgtime=int
Average IOPS calculations over the given time in milliseconds.
Default: 500ms.
create_serialize=bool
If true, serialize file creation for the jobs. Default: true.
create_fsync=bool
fsync(2) data file after creation. Default: true.
create_on_open=bool
If true, the files are not created until they are opened for IO
by the job.
create_only=bool
If true, fio will only run the setup phase of the job. If files
need to be laid out or updated on disk, only that will be done.
The actual job contents are not executed.
allow_file_create=bool
If true, fio is permitted to create files as part of its work‐
load. This is the default behavior. If this option is false,
then fio will error out if the files it needs to use don't
already exist. Default: true.
allow_mounted_write=bool
If this isn't set, fio will abort jobs that are destructive (eg
that write) to what appears to be a mounted device or partition.
This should help catch creating inadvertently destructive tests,
not realizing that the test will destroy data on the mounted
file system. Default: false.
pre_read=bool
If this is given, files will be pre-read into memory before
starting the given IO operation. This will also clear the
invalidate flag, since it is pointless to pre-read and then drop
the cache. This will only work for IO engines that are seekable,
since they allow you to read the same data multiple times. Thus
it will not work on eg network or splice IO.
unlink=bool
Unlink job files when done. Default: false.
loops=int
Specifies the number of iterations (runs of the same workload)
of this job. Default: 1.
verify_only=bool
Do not perform the specified workload, only verify data still
matches previous invocation of this workload. This option allows
one to check data multiple times at a later date without over‐
writing it. This option makes sense only for workloads that
write data, and does not support workloads with the time_based
option set.
do_verify=bool
Run the verify phase after a write phase. Only valid if verify
is set. Default: true.
verify=str
Method of verifying file contents after each iteration of the
job. Each verification method also implies verification of spe‐
cial 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 sup‐
ported by the system.
meta This option is deprecated, since now meta informa‐
tion is included in generic verification header
and meta verification happens by default. For
detailed information see the description of the
verify=str setting. This option is kept because of
compatibility's sake with old configurations. Do
not use it.
pattern
Verify a strict pattern. Normally fio includes a
header with some basic information and checksum‐
ming, but if this option is set, only the specific
pattern set with verify_pattern is verified.
null Pretend to verify. Used for testing internals.
This option can be used for repeated burn-in tests of a system
to make sure that the written data is also correctly read back.
If the data direction given is a read or random read, fio will
assume that it should verify a previously written file. If the
data direction includes any form of write, the verify will be of
the newly written data.
verifysort=bool
If true, written verify blocks are sorted if fio deems it to be
faster to read them back in a sorted manner. Default: true.
verifysort_nr=int
Pre-load and sort verify blocks for a read workload.
verify_offset=int
Swap the verification header with data somewhere else in the
block before writing. It is swapped back before verifying.
verify_interval=int
Write the verification header for this number of bytes, which
should divide blocksize. Default: blocksize.
verify_pattern=str
If set, fio will fill the io buffers with this pattern. Fio
defaults to filling with totally random bytes, but sometimes
it's interesting to fill with a known pattern for io verifica‐
tion 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 writ‐
ten and then verifyied back, e.g.:
verify_pattern=%o
Or use combination of everything:
verify_pattern=0xff%o"abcd"-21
verify_fatal=bool
If true, exit the job on the first observed verification fail‐
ure. 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 sepa‐
rate 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 run‐
ning.
verify_async_cpus=str
Tell fio to set the given CPU affinity on the async IO verifica‐
tion threads. See cpus_allowed for the format used.
verify_backlog=int
Fio will normally verify the written contents of a job that uti‐
lizes verify once that job has completed. In other words, every‐
thing 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 ver‐
ify_backlog_batch is less than verify_backlog then not all
blocks will be verified, if verify_backlog_batch is larger than
verify_backlog, some blocks will be verified more than once.
trim_percentage=int
Number of verify blocks to discard/trim.
trim_verify_zero=bool
Verify that trim/discarded blocks are returned as zeroes.
trim_backlog=int
Trim after this number of blocks are written.
trim_backlog_batch=int
Trim this number of IO blocks.
experimental_verify=bool
Enable experimental verification.
verify_state_save=bool
When a job exits during the write phase of a verify workload,
save its current state. This allows fio to replay up until that
point, if the verify state is loaded for the verify read phase.
verify_state_load=bool
If a verify termination trigger was used, fio stores the current
write state of each thread. This can be used at verification
time so that fio knows how far it should verify. Without this
information, fio will run a full verification pass, according to
the settings in the job file used.
stonewall , wait_for_previous
Wait for preceding jobs in the job file to exit before starting
this one. stonewall implies new_group.
new_group
Start a new reporting group. If not given, all jobs in a file
will be part of the same reporting group, unless separated by a
stonewall.
numjobs=int
Number of clones (processes/threads performing the same work‐
load) of this job. Default: 1.
group_reporting
If set, display per-group reports instead of per-job when
numjobs is specified.
thread Use threads created with pthread_create(3) instead of processes
created with fork(2).
zonesize=int
Divide file into zones of the specified size in bytes. See
zoneskip.
zonerange=int
Give size of an IO zone. See zoneskip.
zoneskip=int
Skip the specified number of bytes when zonesize bytes of data
have been read.
write_iolog=str
Write the issued I/O patterns to the specified file. Specify a
separate file for each job, otherwise the iologs will be inter‐
spersed and the file may be corrupt.
read_iolog=str
Replay the I/O patterns contained in the specified file gener‐
ated by write_iolog, or may be a blktrace binary file.
replay_no_stall=int
While replaying I/O patterns using read_iolog the default behav‐
ior 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 behav‐
ior is to replay the IOPS onto the major/minor device that each
IOP was recorded from. Setting replay_redirect causes all IOPS
to be replayed onto the single specified device regardless of
the device it was recorded from.
replay_align=int
Force alignment of IO offsets and lengths in a trace to this
power of 2 value.
replay_scale=int
Scale sector offsets down by this factor when replaying traces.
per_job_logs=bool
If set, this generates bw/clat/iops log with per file private
filenames. If not set, jobs with identical names will share the
log filename. Default: true.
write_bw_log=str
If given, write a bandwidth log of the jobs in this job file.
Can be used to store data of the bandwidth of the jobs in their
lifetime. The included fio_generate_plots script uses gnuplot to
turn these text files into nice graphs. See write_lat_log for
behaviour of given filename. For this option, the postfix is
_bw.x.log, where x is the index of the job (1..N, where N is the
number of jobs). If per_job_logs is false, then the filename
will not include the job index.
write_lat_log=str
Same as write_bw_log, but writes I/O completion latencies. If
no filename is given with this option, the default filename of
"jobname_type.x.log" is used, where x is the index of the job
(1..N, where N is the number of jobs). Even if the filename is
given, fio will still append the type of log. If per_job_logs is
false, then the filename will not include the job index.
write_iops_log=str
Same as write_bw_log, but writes IOPS. If no filename is given
with this option, the default filename of "jobname_type.x.log"
is used, where x is the index of the job (1..N, where N is the
number of jobs). Even if the filename is given, fio will still
append the type of log. If per_job_logs is false, then the file‐
name will not include the job index.
log_avg_msec=int
By default, fio will log an entry in the iops, latency, or bw
log for every IO that completes. When writing to the disk log,
that can quickly grow to a very large size. Setting this option
makes fio average the each log entry over the specified period
of time, reducing the resolution of the log. Defaults to 0.
log_offset=bool
If this is set, the iolog options will include the byte offset
for the IO entry as well as the other data values.
log_compression=int
If this is set, fio will compress the IO logs as it goes, to
keep the memory footprint lower. When a log reaches the speci‐
fied size, that chunk is removed and compressed in the back‐
ground. 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 log‐
ging ends up consuming most of the system memory. So pick your
poison. The IO logs are saved normally at the end of a run, by
decompressing the chunks and storing them in the specified log
file. This feature depends on the availability of zlib.
log_compression_cpus=str
Define the set of CPUs that are allowed to handle online log
compression for the IO jobs. This can provide better isolation
between performance sensitive jobs, and background compression
work.
log_store_compressed=bool
If set, fio will store the log files in a compressed format.
They can be decompressed with fio, using the --inflate-log com‐
mand line parameter. The files will be stored with a .fz suf‐
fix.
block_error_percentiles=bool
If set, record errors in trim block-sized units from writes and
trims and output a histogram of how many trims it took to get to
errors, and what kind of error was encountered.
disable_lat=bool
Disable measurements of total latency numbers. Useful only for
cutting back the number of calls to gettimeofday(2), as that
does impact performance at really high IOPS rates. Note that to
really get rid of a large amount of these calls, this option
must be used with disable_slat and disable_bw as well.
disable_clat=bool
Disable measurements of completion latency numbers. See dis‐
able_lat.
disable_slat=bool
Disable measurements of submission latency numbers. See dis‐
able_lat.
disable_bw_measurement=bool
Disable measurements of throughput/bandwidth numbers. See dis‐
able_lat.
lockmem=int
Pin the specified amount of memory with mlock(2). Can be used
to simulate a smaller amount of memory. The amount specified is
per worker.
exec_prerun=str
Before running the job, execute the specified command with sys‐
tem(3).
Output is redirected in a file called jobname.prerun.txt
exec_postrun=str
Same as exec_prerun, but the command is executed after the job
completes.
Output is redirected in a file called jobname.postrun.txt
ioscheduler=str
Attempt to switch the device hosting the file to the specified
I/O scheduler.
disk_util=bool
Generate disk utilization statistics if the platform supports
it. Default: true.
clocksource=str
Use the given clocksource as the base of timing. The supported
options are:
gettimeofday
gettimeofday(2)
clock_gettime
clock_gettime(2)
cpu Internal CPU clock source
cpu is the preferred clocksource if it is reliable, as it
is very fast
(and fio is heavy on time calls). Fio will automatically use
this clocksource if it's supported and considered reliable on
the system it is running on, unless another clocksource is
specifically set. For x86/x86-64 CPUs, this means supporting TSC
Invariant.
gtod_reduce=bool
Enable all of the gettimeofday(2) reducing options (dis‐
able_clat, disable_slat, disable_bw) plus reduce precision of
the timeout somewhat to really shrink the gettimeofday(2) call
count. With this option enabled, we only do about 0.4% of the
gtod() calls we would have done if all time keeping was enabled.
gtod_cpu=int
Sometimes it's cheaper to dedicate a single thread of execution
to just getting the current time. Fio (and databases, for
instance) are very intensive on gettimeofday(2) calls. With this
option, you can set one CPU aside for doing nothing but logging
current time to a shared memory location. Then the other
threads/processes that run IO workloads need only copy that seg‐
ment, instead of entering the kernel with a gettimeofday(2)
call. The CPU set aside for doing these time calls will be
excluded from other uses. Fio will manually clear it from the
CPU mask of other jobs.
ignore_error=str
Sometimes you want to ignore some errors during test in that
case you can specify error list for each error type.
ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
errors for given error type is separated with ':'. Error may be
symbol ('ENOSPC', 'ENOMEM') or an integer.
Example: ignore_error=EAGAIN,ENOSPC:122 .
This option will ignore EAGAIN from READ, and ENOSPC and
122(EDQUOT) from WRITE.
error_dump=bool
If set dump every error even if it is non fatal, true by
default. If disabled only fatal error will be dumped
profile=str
Select a specific builtin performance test.
cgroup=str
Add job to this control group. If it doesn't exist, it will be
created. The system must have a mounted cgroup blkio mount
point for this to work. If your system doesn't have it mounted,
you can do so with:
# mount -t cgroup -o blkio none /cgroup
cgroup_weight=int
Set the weight of the cgroup to this value. See the documenta‐
tion that comes with the kernel, allowed values are in the range
of 100..1000.
cgroup_nodelete=bool
Normally fio will delete the cgroups it has created after the
job completion. To override this behavior and to leave cgroups
around after the job completion, set cgroup_nodelete=1. This can
be useful if one wants to inspect various cgroup files after job
completion. Default: false
uid=int
Instead of running as the invoking user, set the user ID to this
value before the thread/process does any work.
gid=int
Set group ID, see uid.
unit_base=int
Base unit for reporting. Allowed values are:
0 Use auto-detection (default).
8 Byte based.
1 Bit based.
flow_id=int
The ID of the flow. If not specified, it defaults to being a
global flow. See flow.
flow=int
Weight in token-based flow control. If this value is used, then
there is a flow counter which is used to regulate the proportion
of activity between two or more jobs. fio attempts to keep this
flow counter near zero. The flow parameter stands for how much
should be added or subtracted to the flow counter on each itera‐
tion 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 laten‐
cies 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, --per‐
centile_list=99.5:99.9 will cause fio to report the values of
completion latency below which 99.5% and 99.9% of the observed
latencies fell, respectively.
Ioengine Parameters List
Some parameters are only valid when a specific ioengine is in use.
These are used identically to normal parameters, with the caveat that
when used on the command line, they must come after the ioengine.
(cpu)cpuload=int
Attempt to use the specified percentage of CPU cycles.
(cpu)cpuchunks=int
Split the load into cycles of the given time. In microseconds.
(cpu)exit_on_io_done=bool
Detect when IO threads are done, then exit.
(libaio)userspace_reap
Normally, with the libaio engine in use, fio will use the
io_getevents system call to reap newly returned events. With
this flag turned on, the AIO ring will be read directly from
user-space to reap events. The reaping mode is only enabled when
polling for a minimum of 0 events (eg when iodepth_batch_com‐
plete=0).
(net,netsplice)hostname=str
The host name or IP address to use for TCP or UDP based IO. If
the job is a TCP listener or UDP reader, the hostname is not
used and must be omitted unless it is a valid UDP multicast
address.
(net,netsplice)port=int
The TCP or UDP port to bind to or connect to. If this is used
with numjobs to spawn multiple instances of the same job type,
then this will be the starting port number since fio will use a
range of ports.
(net,netsplice)interface=str
The IP address of the network interface used to send or receive
UDP multicast packets.
(net,netsplice)ttl=int
Time-to-live value for outgoing UDP multicast packets. Default:
1
(net,netsplice)nodelay=bool
Set TCP_NODELAY on TCP connections.
(net,netsplice)protocol=str, proto=str
The network protocol to use. Accepted values are:
tcp Transmission control protocol
tcpv6 Transmission control protocol V6
udp User datagram protocol
udpv6 User datagram protocol V6
unix UNIX domain socket
When the protocol is TCP or UDP, the port must also be given, as
well as the hostname if the job is a TCP listener or UDP reader.
For unix sockets, the normal filename option should be used and
the port is invalid.
(net,netsplice)listen
For TCP network connections, tell fio to listen for incoming
connections rather than initiating an outgoing connection. The
hostname must be omitted if this option is used.
(net,pingpong)=bool
Normally a network writer will just continue writing data, and a
network reader will just consume packets. If pingpong=1 is set,
a writer will send its normal payload to the reader, then wait
for the reader to send the same payload back. This allows fio
to measure network latencies. The submission and completion
latencies then measure local time spent sending or receiving,
and the completion latency measures how long it took for the
other end to receive and send back. For UDP multicast traffic
pingpong=1 should only be set for a single reader when multiple
readers are listening to the same address.
(net,window_size)=int
Set the desired socket buffer size for the connection.
(net,mss)=int
Set the TCP maximum segment size (TCP_MAXSEG).
(e4defrag,donorname)=str
File will be used as a block donor (swap extents between files)
(e4defrag,inplace)=int
Configure donor file block allocation strategy
0(default): Preallocate donor's file on init
1: allocate space immediately inside defragment event, and
free right after event
(rbd)rbdname=str
Specifies the name of the RBD.
(rbd)pool=str
Specifies the name of the Ceph pool containing the RBD.
(rbd)clientname=str
Specifies the username (without the 'client.' prefix) used to
access the Ceph cluster.
(mtd)skipbad=bool
Skip operations against known bad blocks.
OUTPUT
While running, fio will display the status of the created jobs. For
example:
Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta
00h:01m:31s]
The characters in the first set of brackets denote the current status
of each threads. The possible values are:
P Setup but not started.
C Thread created.
I Initialized, waiting.
R Running, doing sequential reads.
r Running, doing random reads.
W Running, doing sequential writes.
w Running, doing random writes.
M Running, doing mixed sequential reads/writes.
m Running, doing mixed random reads/writes.
F Running, currently waiting for fsync(2).
V Running, verifying written data.
E Exited, not reaped by main thread.
- Exited, thread reaped.
The second set of brackets shows the estimated completion percentage of
the current group. The third set shows the read and write I/O rate,
respectively. Finally, the estimated run time of the job is displayed.
When fio completes (or is interrupted by Ctrl-C), it will show data for
each thread, each group of threads, and each disk, in that order.
Per-thread statistics first show the threads client number, group-id,
and error code. The remaining figures are as follows:
io Number of megabytes of I/O performed.
bw Average data rate (bandwidth).
runt Threads run time.
slat Submission latency minimum, maximum, average and standard
deviation. This is the time it took to submit the I/O.
clat Completion latency minimum, maximum, average and standard
deviation. This is the time between submission and com‐
pletion.
bw Bandwidth minimum, maximum, percentage of aggregate band‐
width received, average and standard deviation.
cpu CPU usage statistics. Includes user and system time, num‐
ber of context switches this thread went through and num‐
ber of major and minor page faults.
IO depths
Distribution of I/O depths. Each depth includes every‐
thing less than (or equal) to it, but greater than the
previous depth.
IO issued
Number of read/write requests issued, and number of short
read/write requests.
IO latencies
Distribution of I/O completion latencies. The numbers
follow the same pattern as IO depths.
The group statistics show:
io Number of megabytes I/O performed.
aggrb Aggregate bandwidth of threads in the group.
minb Minimum average bandwidth a thread saw.
maxb Maximum average bandwidth a thread saw.
mint Shortest runtime of threads in the group.
maxt Longest runtime of threads in the group.
Finally, disk statistics are printed with reads first:
ios Number of I/Os performed by all groups.
merge Number of merges in the I/O scheduler.
ticks Number of ticks we kept the disk busy.
io_queue
Total time spent in the disk queue.
util Disk utilization.
It is also possible to get fio to dump the current output while it is
running, without terminating the job. To do that, send fio the USR1
signal.
TERSE OUTPUT
If the --minimal / --append-terse options are given, the results will
be printed/appended in a semicolon-delimited format suitable for
scripted use. A job description (if provided) follows on a new line.
Note that the first number in the line is the version number. If the
output has to be changed for some reason, this number will be incre‐
mented by 1 to signify that change. The fields are:
terse version, fio version, jobname, groupid, error
Read status:
Total I/O (KB), bandwidth (KB/s), IOPS, runtime (ms)
Submission latency:
min, max, mean, standard deviation
Completion latency:
min, max, mean, standard deviation
Completion latency percentiles (20 fields):
Xth percentile=usec
Total latency:
min, max, mean, standard deviation
Bandwidth:
min, max, aggregate percentage of total, mean,
standard deviation
Write status:
Total I/O (KB), bandwidth (KB/s), IOPS, runtime (ms)
Submission latency:
min, max, mean, standard deviation
Completion latency:
min, max, mean, standard deviation
Completion latency percentiles (20 fields):
Xth percentile=usec
Total latency:
min, max, mean, standard deviation
Bandwidth:
min, max, aggregate percentage of total, mean,
standard deviation
CPU usage:
user, system, context switches, major page faults, minor
page faults
IO depth distribution:
<=1, 2, 4, 8, 16, 32, >=64
IO latency distribution:
Microseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
Milliseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000,
2000, >=2000
Disk utilization (1 for each disk used):
name, read ios, write ios, read merges, write merges,
read ticks, write ticks, read in-queue time, write in-
queue time, disk utilization percentage
Error Info (dependent on continue_on_error, default off):
total # errors, first error code
text description (if provided in config - appears on newline)
CLIENT / SERVER
Normally you would run fio as a stand-alone application on the machine
where the IO workload should be generated. However, it is also possible
to run the frontend and backend of fio separately. This makes it possi‐
ble to have a fio server running on the machine(s) where the IO work‐
load should be running, while controlling it from another machine.
To start the server, you would do:
fio --server=args
on that machine, where args defines what fio listens to. The arguments
are of the form 'type:hostname or IP:port'. 'type' is either 'ip' (or
ip4) for TCP/IP v4, 'ip6' for TCP/IP v6, or 'sock' for a local unix
domain socket. 'hostname' is either a hostname or IP address, and
'port' is the port to listen to (only valid for TCP/IP, not a local
socket). Some examples:
1) fio--server
Start a fio server, listening on all interfaces on the default port
(8765).
2) fio --server=ip:hostname,4444
Start a fio server, listening on IP belonging to hostname and on
port 4444.
3) fio --server=ip6:::1,4444
Start a fio server, listening on IPv6 localhost ::1 and on port
4444.
4) fio --server=,4444
Start a fio server, listening on all interfaces on port 4444.
5) fio --server=1.2.3.4
Start a fio server, listening on IP 1.2.3.4 on the default port.
6) fio --server=sock:/tmp/fio.sock
Start a fio server, listening on the local socket /tmp/fio.sock.
When a server is running, you can connect to it from a client. The
client is run with:
fio--local-args --client=server --remote-args <job file(s)>
where --local-args are arguments that are local to the client where it
is running, 'server' is the connect string, and --remote-args and <job
file(s)> are sent to the server. The 'server' string follows the same
format as it does on the server side, to allow IP/hostname/socket and
port strings. You can connect to multiple clients as well, to do that
you could run:
fio --client=server2 --client=server2 <job file(s)>
If the job file is located on the fio server, then you can tell the
server to load a local file as well. This is done by using --remote-
config:
fio --client=server --remote-config /path/to/file.fio
Then fio will open this local (to the server) job file instead of being
passed one from the client.
If you have many servers (example: 100 VMs/containers), you can input a
pathname of a file containing host IPs/names as the parameter value for
the --client option. For example, here is an example "host.list" file
containing 2 hostnames:
host1.your.dns.domain
host2.your.dns.domain
The fio command would then be:
fio --client=host.list <job file>
In this mode, you cannot input server-specific parameters or job files,
and all servers receive the same job file.
In order to enable fio--client runs utilizing a shared filesystem from
multiple hosts, fio--client now prepends the IP address of the server
to the filename. For example, if fio is using directory /mnt/nfs/fio
and is writing filename fileio.tmp, with a --client hostfile containing
two hostnames h1 and h2 with IP addresses 192.168.10.120 and
192.168.10.121, then fio will create two files:
/mnt/nfs/fio/192.168.10.120.fileio.tmp
/mnt/nfs/fio/192.168.10.121.fileio.tmp
AUTHORSfio was written by Jens Axboe <jens.axboe@oracle.com>, now Jens Axboe
<axboe@fb.com>.
This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au>
based on documentation by Jens Axboe.
REPORTING BUGS
Report bugs to the fio mailing list <fio@vger.kernel.org>. See README.
SEE ALSO
For further documentation see HOWTO and README.
Sample jobfiles are available in the examples directory.
User Manual December 2014 fio(1)
