Cyrus lagging accepting IMAP connections

[Rick Kunkel]

Hello all,

I'm new to Cyrus.  Historically, I've used Qpopper, Sendmail, and UW IMAP. 
We recently switched to Cyrus for IMAP.  It came highly recommended...

We've got this on a darned burly machine, running some very recent version 
of Debian, with a fast CPU, 4GB RAM, and fast SAS drives.  When testing 
the thing, before it went into production, everything worked awesomely. 
However, having loaded it with 2300 users, it's suddenly acting 
erratically.  (Incidentally, of the 2300 users, almost all are POP users, 
which seems to be working fine.  A few hundred -- at most -- are IMAP, and 
they are split between squirrelmail users and a handful that use standard 
MUAs.)

The server acts as if it's low on resources or something, or has hit some 
kind of connection limit.  It's speedy as heck WHEN it does it what's it's 
supposed to, but that initial connection is sketchy.  For the first 30 
seconds after you restart it, it's generally good, but it goes downhill 
from there.

Testing with telnet exhibits this behavior.  Here's a sample session...

# telnet mail 143
Trying xxx.xxx.xxx.xxx...
Connected to mail.
Escape character is '^]'.


And then it just kinda sits.  Sometimes, after 30 seconds or so

* OK mail Cyrus IMAP4 v2.2.13-Debian-2.2.13-10 server ready


We're currently using the following line in cyrus.conf for imapd:

imap	cmd="imapd" listen="imap" prefork=1


We've messed with tons of different settings here, to little avail.

There don't seem to be any salient log entries.

Anyone have any ideas?

Thanks,

Rick Kunkel