Benchmark, Bonnie++, FIO, FreeBSD, GSoC, IOZONE, RTEMS, Software

Comparing IO benchmarks: FIO, IOZONE and BONNIE++

IO benchmarks refer to the computerized test for measuring various properties of a IO device under various conditions. Various properties includes Read/Write speed, IOPS, seek time etc and various conditions refers to random/sequential reads/writes, block size used by the filesystem, buffer cache size etc. There are various IO benchmarks available online, but the top 3 opensource IO benchmarks, in my view includes FIO, IOZONE and BONNIE++. There are several pros and cons for each of them, which we will be discussing in this blog post.

Fio (Documentation, Repository)

fio is an I/O tool meant to be used both for benchmark and stress/hardware verification. It has support for 13 different types of I/O engines (sync, mmap, libaio, posixaio, SG v3, Omega Replica Watches splice, null, network, syslet, guasi, solarisaio, and more), I/O priorities (for newer Linux kernels), rate I/O, forked or threaded jobs, and much more. It supports Linux, FreeBSD, NetBSD, OS X, OpenSolaris, AIX, HP-UX, and Windows.

Example: sudo fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=randwrite --bs=4k --direct=0 --size=512M --numjobs=2 --runtime=240 --group_reporting


Greatly improved disk I/O benchmark based on the code for Bonnie by Tim Bray. Bonnie++, rewritten in C++ by Russell Coker (, adds the facility to test more than 2Gb of storage on 32-bit machines, and tests for file create(), stat(), unlink() operations.

Example: bonnie++ -d /tmp -s 4G -n 0 -m TEST -f -b -u udit

IOzone (Documentation, Repository)

The benchmark generates and measures a variety of file operations. IOzone is useful for performing broad filesystem analysis of a vendor’s computer platform. It can also be used for NFS performance testing and the latest version now supports cluster testing as well. IOzone had been ported to numerous UNIX OSes and Windows NT.

Example: iozone -e -I -a -s 100M -r 4k -r 512k -r 16M -R -i 0 -i 1 -i 2 -f /dev/sdda0s1


Activeness in
High Very High Moderate
I/O buffer types
direct, buffered direct, atomic, buffered Direct, Buffered
IO R/W available Read, write, random read,
random write, reread, rewrite,
strided read/write, Random Mix,
Backwards read, Fread, Fwrite, Freread,
Read, write, random read/write
trim, random trim, readwrite, random
readwrite, trimwrite
Read/write, random
Special type of IO Mmap, Async I/O sync, psync, vsync, pvsync, pvsync2, libaio,
posixaio, solarisaio, windosaio, mmap, sg, net,
netsplice, cpuio, guasi, rdma, falloc, ftruncate,
e4defrag, rados, rbd, gfapi, gfapi_async, and lot more.
Types of random
datasets generated
for random R/W
Uniform Uniform, gaussian, pareto, ziph, zoned,
absolute zoned
Random number
generating engine
Fisher yates algo tausworthe, lfsr, tausworthe64
Flexibility Quite customizable ‘Flexibility’ is in its name! It’s Highly configurable,
with number of available modes.
mostly automatic. Very
less configurable
License type customized GPLv2 GPLv2
Benchmark type Filesystem benchmark that can benchmark
Storage devices too
Specifically built for benchmarking storage device,
but can be used for filesystem benchmarking too
Filesystem benchmark
Statistics available
as output
Amount of I/O generated in KBps Max. Min. Avg latency with standard deviation, Average
bandwidth, IOPS , amount of I/O generated in KBps, average
queue depth
Amount of I/O generated in MBps
available in CSV format
Others Stonewalling to synchronize threads Pattern verification available; user configurable
error handling, clock settings etc;


Although it’s pretty clear from the above comparison that Fio fits perfect for benchmarking storage devices, IOzone and Bonnie++ are still used for applications which doesn’t require too many features, just simple read/write. quick benchmarking. Further, for any naive user, getting grip on IOzone is much much easier then struggling with complex features of Fio.

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5 thoughts on “Comparing IO benchmarks: FIO, IOZONE and BONNIE++

    1. Sure. Now my GSoC work is almost done, I can refine/enhance this posts with other benchmarking tools available on FreeBSD

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