Just in case it is of general interest: ZFS mirroring was the culprit in our case
vbfox at ucdavis.edu
Tue Nov 13 10:59:16 EST 2007
Can you expand on this, like a LOT?
I recall a while ago you brought up some performance issues and
said you had found hacks for them. Were those issues actually unresolved
or are you talking about something else? I don't see any recent posts by
you about problems with your Cyrus install.
I'm struggling to see the mechanism by which mirroring creates a problem.
Were you resilvering at the time?
Pascal Gienger wrote:
> Our latency problems went away like a miracle when we detached one half of
> the mirror (so it is no more a mirror).
> Read-Rates are doubled (not per device, the total read rate!), latency is
> cut off. No more latency problems.
> When attaching the volume again, resilvering puts the system to a halt -
> reads and writes do block for seconds (!). We will go on directly with Sun
> to solve the problem. Their "lowest I/O-priority to resilver disks" does
> not seem to be effective. It really blocks the kernel and you end up with
> thousand locks in "zfs_zget".
> We have two SAN volumes in different buildings which are NOT the
> bottleneck, tests show it.
> Cyrus Home Page: http://cyrusimap.web.cmu.edu/
> Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
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