[imp] IMP performance under load

[Chris Crowley]

Stephen wrote:
> Any information would be of great assistance

I ran IMP on a IBM Netfinity single 500Mhz processor with 128MB memory. This
was too small for even the test group of users it was running for. I would
regularly see very high load (up to 100) on this machine.  I had a script
which would sense this condition, stop the apache server, restart MySql,
then restart apache. This was sufficient to bring the load back into line
until the next time it went out of control

Currently, the Apache / MySql server that Tulane uses is not the bottleneck
in IMP's performance. The current bottleneck is the mailserver. You spend
some time considering the additional load any webmail client will place on
your mailserver.  The Sun Solaris 8 machine that we run IMP on weighs in
with 4 - UltraSPARC-II and 1 Gig memory.  It rarely exceeds a load of 1.0 .
There are other webservices running on the same machine beside IMP. All IMP
connections are made via SSL.

We have approximately 2,000 unique logins per day from a user base of
approximately 20,000 users. So, I am very interested in performance
improvements that could be made because a large number of our users still
use Pine. I suspect the newer users will be more inclined to use webmail.

The biggest performance loss is currently the IMAP server. We are currently
looking at improvements for IMAP, any suggestions on this front are welcome.
We also use sendmail, and POP3, so any IMAP servers would need to use a file
format that is compatible.  I have read that indexed files will provide much
quicker recall of user information.  But we have not yet determined a
comprehensive plan for server improvements. Disk array on the mailserver
should be optimized, too.

One reference of sendmail tuning suggestions:
http://www.shub-internet.org/brad/papers/sendmail-tuning/

Mail server performance is very important to the IMP implementation, I am
surprised there is less discussion of it on the list.

Chris