LARGE single-system Cyrus installs?

[Michael Bacon]

--On Friday, November 16, 2007 7:39 AM +0100 Pascal Gienger 
<Pascal.Gienger at uni-konstanz.de> wrote:

> Solaris 10 does this in my case. Via dtrace you'll see that open() on the
> mailboxes.db and read-calls do not exceed microsecond ranges.
> mailboxes.db  is not the problem here. It is entirely cached and rarely
> written  (creating, deleting and moving a mailbox).

This is where I think the actual user count may really influence this 
behavior.  On our system, during heavy times, we can see writes to the 
mailboxes file separated by no more than 5-10 seconds.

If you're constantly freezing all cyrus processes for the duration of those 
writes, and those writes are taking any appreciable time at all, you're 
going to have a stuttering server with big load averages.

Again, it's not I/O throughput to be worried about here -- it's latency. 
If you don't have write caches in front of your disk, even with RAID you're 
still at the mercy of drive latency in the millisecond range.  Not a 
problem if those writes are once every five minutes, but if you're at peak 
load on a big system and seeing them every couple of seconds, that's brutal.

-Michael