SUMMARY (partial): ZFS fragmentation

From: joe fletcher <>
Date: Tue Aug 02 2011 - 17:29:55 EDT

Thanks to all those who responded.

In terms of an actual defragmenter it would appear that one won't be available
in the near future.

By way of a solution it appears the best workaround (in some circumstances) is
the use of separate dedicated ZIL devices. I've added these to a couple of
systems and we'll monitor to see if this slows the performance degradation.

There does seem to be a general concensus that ZFS is not best suited to
database applications but unfortunately for us these are the system where
we're seeking to use the general performance gains that ZFS offers.

We'll keep working at it and hopefully Oracle will come up with a defragger.




From: on behalf of joe fletcher
Sent: Mon 01/08/2011 17:39
Subject: ZFS fragmentation


Got an app that appears to be causing fragmentation on a ZFS file system.
Reading suggest there's no defragger for ZFS (assuming this is the problem).
Reading also suggests that a defragger will be coming "real soon now" but
"real soon" seems to have been over 3 years now.

Assuming fragmentation is the problem, is there a fix, other than copying the
contents of the file sys to a new volume every night?


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Received on Tue Aug 2 17:30:45 2011

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