LARGE single-system Cyrus installs?

[Vincent Fox]

Eric Luyten wrote:
> Another thought : if your original problem is related to a locking issue
> of shared resources, visible upon imapd process termination, the rate of
> writing new messages to the spool does not need to be a directly contri-
> buting factor.
> Were you experiencing the load problem while (briefly) halting deliveries
> to the mail spool ?
>   

Yep we tried stopping mail delivery.

If there's something that 3 admins could do to alleviate load we did it.

The bigger problem I am seeing is that Cyrus doesn't in our
usage seem to ramp load smoothly or even predictably.  It goes
fine up to a certain point, and then you hit a brick wall without
very much in the way of warning.  You add that small chunk of
extra users or load and suddenly everything goes to hell.  Keeping
the user-count per instance appropriate was the only thing we did
over multiple days of desperate "try this" that did the job.

A generous engineering cushion of capacity seems more critical than usual.