LARGE single-system Cyrus installs?

Pascal Gienger Pascal.Gienger at
Thu Nov 22 02:54:03 EST 2007

Vincent Fox <vbfox at> wrote:

> This thought has occurred to me:
> ZFS prefers reads over writes in it's scheduling.
> I think you can see where I'm going with this.  My WAG is something
> related to Pascal's, namely latency.  What if my write requests to
> mailboxes.db
> or deliver.db start getting stacked up, due to the favoritism shown to
> reads?

I got substantial benefits from setting compression=on and recordsize=32K 
on the filesystem where deliver.db resides. After talking with our SAN 
staff it showed up that storage was our problem - it has problems with 
concurrent write and read calls, the system won't answer read requests if 
the write channel is "full". I don't know whether it is a firmwire issue or 
a non-capability of the storage system.

Lowering ZFS' recordsize and activating compression on that partition cut 
down i/o rate and things are going normal here again.

Thanks to all who helped!


PS: The mirror resilvering problem was a misconfiguration of a brocade 
switch... Sometimes you don't see the forest due to so many trees (german 
proverb, "Man sieht den Wald vor lauter Bäumen nicht")...

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