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

--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.

--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'.

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

--help
    Display usage information and exit.

--version
    Display version information and exit.

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. job files.

  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 Integer: a whole number, possibly negative. If prefixed with `0x', the value is assumed to be base 16 (hexadecimal).

siint
    SI integer: a whole number, possibly containing a suffix denoting the base unit of the value. Accepted suffixes are `k', 'M' and 'G', denoting kilo (1024), mega (1024*1024) and giga (1024*1024*1024) respectively.

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'.

  Parameter List

name=str
    May be used to override the job name. On the command line, this paramter 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 used is `net', filename is the host and port to connect to in the format host/port. 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.

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  Mixed sequential reads and writes.

        randrw
            Mixed random reads and writes.

    For mixed I/O, the default split is 50/50. For random I/O, the number of I/Os to perform before getting a new offset can be specified by appending `:int' to the pattern type. The default is 1.

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

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

size=siint
    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 nr_files and filesize options are given, this amount will be divided between the available files for the job.

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=siint, bs=siint
    Block size for I/O units. Default: 4k. Values for reads and writes can be specified seperately in the format read,write, either of which may be empty to leave that value at its default.

blocksize_range=irange, bsrange=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, but can be specified seperately (see blocksize).

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.

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

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).

    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.

        libaio
            Linux native asynchronous I/O.

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

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

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

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

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

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

        net Transfer over the network. filename must be set appropriately to `host/port' regardless of data direction. If receiving, only the port argument is used.

        netsplice
            Like net, but uses splice(2) and vmsplice(2) to map data and send/receive.

        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>.

        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. Default: 1.

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

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

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

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.

rwmixcycle=int
    How many milliseconds before switching between reads and writes for a mixed workload. Default: 500ms.

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 wrmixwrite are given and do not sum to 100%, the latter of the two overrides the first. 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 without looking at past I/O history. This parameter is mutually exclusive with verify.

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 to this number of KiB/s.

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.

rate_iops=int
    Cap the bandwidth to this number of IOPS. 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.

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.

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.

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

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.

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

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

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 crc64 crc7 sha256 sha512
            Store appropriate checksum in the header of each block.

        meta
            Write extra information about each I/O (timestamp, block number, etc.). The block number is verified.

        pattern
            Fill I/O buffers with a specific pattern that is used to verify. The pattern is specified by appending `:int' to the parameter. int cannot be larger than 32-bits.

        null
            Pretend to verify. Used for testing internals.

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

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

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

stonewall
    Wait for preceeding 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=siint
    Divide file into zones of the specified size in bytes. See zoneskip.

zoneskip=siint
    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.

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

write_bw_log
    If given, write bandwidth logs of the jobs in this file.

write_lat_log
    Same as write_bw_log, but writes I/O completion latencies.

lockmem=siint
    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.

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.

TERSE OUTPUT
If the --minimal option is given, the results will be printed in a semicolon-delimited format suitable for scripted use. The fields are:

    jobname, groupid, error

    Read status:
        KiB I/O, bandwidth (KiB/s), runtime (ms)

        Submission latency:
            min, max, mean, standard deviation
        Completion latency:
            min, max, mean, standard deviation
        Bandwidth:
            min, max, aggregate percentage of total, mean, standard deviation

    Write status:
        KiB I/O, bandwidth (KiB/s), runtime (ms)

        Submission latency:
            min, max, mean, standard deviation
        Completion latency:
            min, max, mean, standard deviation
        Bandwidth:
            min, max, aggregate percentage of total, mean, standard deviation

    CPU usage:
        user, system, context switches

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

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

    text description

AUTHORS
fio was written by Jens Axboe <jens.axboe@oracle.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-devel@kernel.dk>. See README.

SEE ALSO
For further documentation see HOWTO and README.
Sample jobfiles are available in the examples directory.