>If someone else thinks I'm barking up the wrong tree, please do let me know.
>For reference, the system in question is a Pentium-Pro 200, 64 MB RAM, 4.2
>gb EIDE boot disk, and 8 gb EIDE data disk. IMAP server is imap-uw 4.5 from
>pkgsrc. Userload is about 20-30 people, with mailboxes around 5-10 megs each


Uh, sounds More likley to be a network problem than a disk problem.
What kind of ethernet card do you have (a) in the PPro server, (b) on
the IMAP clients?  If you see long delays, retransmits, or If any of
them have ne2000 cards, toss 'em out and try an Intel pro/100, a
Tulip-based card, or a 3com.

If you want to acutally diagnose first, I'd try a tcpdump on the
server, using -w, and post-process the tcpdump file afterward to look
for idle periods and retransmissions (e.g., if the \clients use TCP,
use tcptrace and xplot; tcp retransmits show up in red in the
*_tsg.xpl files).