"Jeffrey J. Kosowsky" <backuppc@kosowsky.org> wrote on 02/23/2011 10:46:54 AM:

> Are you using lvm snapshots?
> It seems that some of my terribly slow recent performance has been due
> to having lvm snapshots. I saw a site that claimed lvm snapshots in
> practice can degrade write performance up to 20-30x...

This is mostly true when your log file is on the same spindle as the LV you're snapshotting.  That should be considered an absolute no-no.  You get the type of performance dropoff you're talking about.  LVM snapshots pretty much require a dedicated drive for the log.  Or drives:  if the volume you're snapshotting is a, say, 6-disk RAID array, and you give only a single drive for the log, everything gets bottlenecked by the log drive.

Timothy J. Massey
Out of the Box Solutions, Inc.
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