[imp] Horde/IMP performance and system requirements (50k+ accounts)

[Janne Peltonen]

Hi!

We've been running IMP here at the University of Helsinki since 2001,
and performed a major upgrade last summer, straight into Horde Webmail
Edition 1.1.1. Since then, there has been no end of problems we've been
running into, most notably all kinds of performance problems
- so much so that we've been considering moving out of Horde/IMP
altogether. At least my boss is getting convinved that Horde just
doesn't work.

But to concentrate on performance. The old IMP hopped along nicely on
three load balanced x86 servers, with 2-4 cores at 2,3 GHz and 2-4 GB
RAM, running Linux - the load was negligible (actually, the server with
4 cores and 4GB could handle all the load if need be). And the load on
the database server was negligible. Now, we have three xen virtual
servers, each with 4 cores @ 2,3 GHz (64 bit) and 6 GB memory, and they
tend to choke at peak load - during the day, the load is always
noticeable, it takes a couple seconds for each request to complete.
Also, the mysql server tends to run with the mysqld process occupying
one processor completely and hogging all the memory it can get (2GB, the
server running on a 32 bit system). We had to disable Kronolith, Nag and
Mnemo completely, because they just completely choked the mysql server.

We are using all kinds of performance tweaks we could find information
on, we are using a php cache (apc) and so on, but still the problems
persist... So I was wondering if there are other people using a new
Horde Webmail Edition in a similar setting: a university, ~50k accounts
(including students & staff), peak concurrent users ~5000, peak
logins/minute ~160. If anyone is, we'd like to hear about your
performance experiences and also, what kind of hardware / OS you are
running. Also, if there were any specific tricks that helped you reduce
the server load, we'd love to hear about them.

Thanks for any answers.


--Janne Peltonen
University of Helsinki
-- 
Janne Peltonen <janne.peltonen at helsinki.fi> PGP Key ID: 0x9CFAC88B
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