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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