Speed Difference Nas4Free/FreeNAS/ZoL

[trendco]

Hi,

i have a massive Speed difference with the same Pool on different Systems.
I created the Pool on Nas4Free, 2x Hitachi 3TB -> mirror
I tested the Write/Read with DD:

dd if=/dev/zero of=/mnt/raid1-hd/Data/test.dat bs=2M count=1400
dd if=/mnt/raid1-hd/Data/test.dat of=/dev/null bs=2M

Between write and read Test i rebooted the System and I've done the Tests on each System multiple times:

Nas4Free 9.1.0.1 - Sandstorm (Revision 804)
Write: ~103 MB/Sec
Read: ~105 MB /Sec

FreeNAS 9.1
Write: ~105 MB/Sec
Read: ~155 MB /Sec

Debian Wheezy - ZFS on Linux:
Write: ~105 MB/Sec
Read: ~160 MB /Sec

The Write Speed is almost equal on the Systems. But why is the Read Speed on Nas4Free so slow compared with the Others?
I hvae alredeady tested "kernel tune", but no Difference.

Any Ideas?

[siftu]

Did you enable prefetch in zfskerntune? This seems like the likely cause. If you system has >4GB of RAM the other systems will enable it by default but NAS4Free has is explicitly disabled.

The following shows you how to check.

http://n4f.siftusystems.com/index.php/2 ... it-in-gui/

And here is some performance with it enabled and disabled.

http://n4f.siftusystems.com/index.php/2 ... -prefetch/

Hope that helps.

[trendco]

That's it!

vfs.zfs.prefetch_disable="0"

is the Solution.


I had taken the tuning Parameters from viewtopic.php?f=71&t=1278&p=10011&hilit=tune#p21974 an there is written vfs.zfs.prefetch_disable="1" !?


The DD Speed is ok now, similar to Freenas and ZoL.
But my AFP Speed is the same as befor, see Post viewtopic.php?f=26&t=4736
Also any Ideas?

[dnar]

Just curious, how stable is ZFS on Linux?

[alexey123]

Before check and compare disk speed with dd pls check disk performance with

Code: Select all

diskinfo -ctv /dev/<your disk>

and see output for Transfer rates.
See differences between outside, middle, inside

[trendco]

See my last Post, i had written that the speed is ok now with:

vfs.zfs.prefetch_disable="0"

Now I have only a Problem with AFP Speed -> viewtopic.php?f=26&t=4736