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 win. 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! Bron. ---- 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
