OVH Guides

Test disk speed

Test disk speed

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 walks you through the process of testing the number of input/output operations per second (IOPS) that your disks are able to achieve, whether for instances, or additional disks.


  • An instance
  • An additional disk


The command that you need is not available by default, you will need to install it first:

root@server:~$ apt-get install fio


Command for testing your disks:

root@serveur:~$ 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 You have to adapt the argument --numjobs depending on the number of processing units (CPU) that your instance has. In addition, it is possible to retrieve a list of arguments and their functions directly from the fio guide. To test the performance of an additional disk, you have to run the following command to mount the disk.

root@serveur:~$ cd /mnt/disk


Once you have run this command you will get a result similar to this:

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, 

We are interested in line six of the results 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.

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