LARGE single-system Cyrus installs?

Bron Gondwana brong at
Thu Nov 15 18:39:12 EST 2007

On Thu, Nov 15, 2007 at 01:29:54PM -0500, Wesley Craig wrote:
> On 14 Nov 2007, at 23:15, Vincent Fox wrote:
> > We have all Cyrus lumped in one ZFS pool, with separate filesystems  
> > for
> > imap, mail, sieve, etc.  However, I do have an unused disk in each  
> > array
> > such that I could setup a simple ZFS mirror pair for /var/cyrus/ 
> > imap so
> > that the databases are in their own pools.  Or even I suppose a UFS
> > filesystem with directio and all that jazz set.
> About 30% of all I/O is to mailboxes.db, most of which is read.  I  
> haven't personally deployed a split-meta configuration, but I  
> understand the meta files are similarly heavy I/O concentrators.

Which is a good argument for checkpointing it (gah, hate that term -
it's so non-specific.  I've spent some time working on terminology
maps for this stuff, and "repack" is the current winner, mainly due
to be shorter than the runner up "consolidate")

What was I saying again?  Oh - yes.  Current skiplist metric is that
the mailboxes.db has to be be twice the size of the last checkpointed
size plus 16k before it re-checkpoints.  Given that a checkpoint takes
approximately 2 seconds on our systems, and it means that you're not
seeking all over the place any more, it would almost certainly be a

That said, we don't have a single machine where the memory pressure
is tight enough to ever push mailboxes.db out of the cache, so it's
not ever going to be hitting the disk for reads anyway!


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