[SOLVED] Linux virtual machines poor IO perfomance over SSD

[Jesus Blanco]

Hello,

I have a 5 node cluster with a Dell Compellent sc2020 with 7 SSD disk with mutlipath as storage .

On Windows virtual machines when I do a CrystalDisk benchmark we have a little over 22000 IOPS but when I do a fio test on Linux machines never got over 4800 IOPS.

So in windows the performance its OK, always coud be more but no complaints, but in Linux the performance is poor.

I think the problems is that Linux machine not detecte de virtio disks as SSD disk. If check if the kernel see disks as HD or SSD I always get this:

cat /sys/block/vda/queue/rotational
1
Either if I change this to 0:

echo 0 > /sys/block/vda/queue/rotational

And then do a fio test the result is the same.

Could anyone help me?

Thanks in advance

 

[dietmar]

If you want to compare benchmarks results, its essential to use the same benchmark tool on both systems ...

 

[NewDude]

Yep. Odds are you're measuring different things.

 

[christophe]

Hi,

Some months ago i found a fio wrapper to « emulate » cristal disk mark. On github.

It helps to compare, but be careful.

Christophe.

 

[LnxBil]

You can also use fio on windows. Have you specific multipath configuration on Windows or Linux? Normally, the difference should be negligible.

 

[Jesus Blanco]

Thank you for your answers. Finally I managed to get the performance of the SSD disks by changing the configuration of execution of fio.
Using this config:

[global]
bs=4k
ioengine=libaio
iodepth=32
size=4g
direct=1
runtime=60
directory=/home
filename=ssd.test.file

[seq-read]
rw=read
stonewall

[rand-read]
rw=randread
stonewall

[seq-write]
rw=write
stonewall

[rand-write]
rw=randwrite
stonewall

I have obtained more than 1300MB / s and more than 25000 IOPS.

Thanks again for your help!

 

[flotho]

Thank you for your answers. Finally I managed to get the performance of the SSD disks by changing the configuration of execution of fio.
Using this config:

Hi,

Could you give us some additionnal precisions on which file you modified?

regards