LARGE single-system Cyrus installs?

[Vincent Fox]

To close the loop since I started this thread:

We still haven't finished up the contract to get Sun out here to
get to the REAL bottom of the problem.

However observationally we find that under high email usage that
above 10K users on a Cyrus instance things get really bad.  Like last
week we had a T2000 at about 10,500 users and loads of 5+ and it
was bogging down.  We moved 1K users off bringing it down to
9,500 and loads dropped to around 1.0 and everything is fine.

We have investigated doing this with Solaris Zones with multiple instances
of 5K users each on a single system and it seems like a workable idea.
However the PITA of working out patch procedures for all the zones
and the system itself, and it's cluster partner, seem too intensive.

Our latest line of investigation goes back to the Fastmail suggestion, 
simply
have multiple Cyrus binary instances on a system.  Each running it's own
config and with it's own ZFS filesystems out of the pool to use.
Since we can bring up a virtual interface for each instance we won't even
have to bother with using separate port numbers, etc.