Test disk speed

This guide will show you how to test the number of input/output operations per second (IOPS) that your disks are able to achieve, whether for instances or additional disks.

Last updated 4th January 2022


You'll probably be called upon to check the speed of your disks when you carry out your tests. Whether you want to compare the performance of different disks or just check if they are satisfactory.

This guide will show you how to test the number of input/output operations per second (IOPS) that your disks are able to achieve, whether for instances or additional disks.



Install the test command

The command that you need to test your disk speed is called fio, and is not installed on your server by default.

To install fio, establish an SSH connection to your Instance and then run the following command:

root@server:~$ apt-get install fio

Test your disk speed

To test your disk speed, run the following command:

root@server:~$ fio 
--name=rand-write --ioengine=libaio --iodepth=32 --rw=randwrite --invalidate=1 --bsrange=4k:4k,4k:4k --size=512m --runtime=120 --time_based --do_verify=1 --direct=1 --group_reporting --numjobs=1

Please note that you will need to modify the --numjobs argument to reflect the number of CPUs that your instance has.

You can retrieve a list of arguments and their functions directly from the fio guide.

To test the speed of an additional disk, you will need to mount the disk with the following command:

root@server:~$ cd /mnt/disk

Analyse the data

Once the test is finished, you will get a result similar to the following:

Starting 1 process
test: Laying out IO file(s) (1 file(s) / 1024MB)
Jobs: 1 (f=1): [w(1)] [40.9% done] [0KB/3580KB/0KB /s] [0/895/0 iops] [eta 02m:55s]
test: (groupid=0, jobs=1): err= 0: 
pid=12376: Thu Oct 29 14:46:37 2015
write: io=428032KB, bw=3566.2KB/s, 
iops=891, runt=120031msec
slat (usec): min=4, max=4640, avg=22.57, stdev=62.14
clat (usec): min=299, max=181699, avg=34778.45, stdev=7857.92
lat (usec): min=324, max=181769, 
avg=34801.55, stdev=7843.84
clat percentiles (usec):
| 1.00th=[ 708], 5.00th=[30848], 10.00th=[33536], 20.00th=[34560],
| 30.00th=[35072], 40.00th=[35072], 50.00th=[35072], 60.00th=[35584],
| 70.00th=[36096], 80.00th=[36608], 90.00th=[37632], 95.00th=[39680],
| 99.00th=[47360], 99.50th=[51968], 99.90th=[125440], 99.95th=[146432],
| 99.99th=[181248]
bw (KB /s): min= 2646, max= 4232, 
per=100.00%, avg=3567.77, stdev=136.56
lat (usec) : 500=0.23%, 750=1.26%, 
lat (msec) : 2=0.37%, 4=0.03%, 10=0.01%, 20=0.11%, 50=96.05%
lat (msec) : 100=0.58%, 250=0.14%
cpu : usr=0.34%, sys=1.80%, ctx=9281, 
majf=0, minf=8
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 
8=0.1%, 16=0.1%, 32=100.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 
16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 
16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=0/w=107008/d=0, 
latency : target=0, window=0, percentile=100.00%, depth=32

Run status group 0 (all jobs):
WRITE: io=428032KB, aggrb=3566KB/s, minb=3566KB/s, maxb=3566KB/s, 
mint=120031msec, maxt=120031msec

Disk stats (read/write):
vda: ios=0/300294, merge=0/1455, ticks=0/7431952, in_queue=7433124, 

The line we're interested in is line six, which contains the IOPS:

write: io=428032KB, bw=3566.2KB/s, iops=891, runt=120031msec

We can see that disk performance is approximately 891 IOPS.

Go further

Create and configure an additional disk on an Instance

Add storage space

Join our community of users on https://community.ovh.com/en/.

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