ZFS RaidZ2 with 24 drives?

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Wed Dec 23 21:04:00 UTC 2009


On Wed, 23 Dec 2009, Solon Lutz wrote:

> I opted for two 12-disc raidz2.
> Reasons were: Space is more important than performance.
>
> But performance is very poor - have a look at the iostats - sometimes nothing really seems
> to happen for up to ten seconds, or very little data gets  written. Might this be a problem
> of the amd64 system having only 4GB of RAM? Any tuneable sysctls? Enabling prefetch didn't help...:

The most likely cause is that several of your disks are not performing 
properly.  Perhaps a disk is performing error recovery, or there is a 
bad cable, or maybe even too much chassis vibration.  It only takes 
one pokey disk in a vdev to slow down the whole vdev.  Using 'iostat 
-x 10' while your pool is under continous I/O load may help find the 
pokey disks.

Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/


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