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

[LALOT Dominique]

We are in the way to migrate too, but with less users (25k). But it's not so
much used by students, and most of the staff is using imap clients on their
PC. So we can't compare. Some big french universities are just starting on
that release.
They notice that there is a big difference on the fact we are using dimp
(much more little get).

What you can do, is lock the prefs initial_application and use IMP instead
of DIMP. Another point is alarms.php or reminders.php. I noticed during my
tests that:
reminders.php should be avoided (If you leave it in crontab every 5', it's a
mistake). Jan said it was just for daily summary. As I locked that, only
alarms.php is necessary. But alarms.php also can be a problem, as it runs
every 5 minutes and generates tons of selects. Don't remember exactly but
more than 10k for 4k users.

Also, you'll have to look at mysql. For big databases, you need special
tuning as default values are not good. We are in he way to put (for HA)
another mysql server and we will split the access to several servers.
(replica)

As I reread your mail, look at your SQL setup..

Dom

2009/3/20 Janne Peltonen <janne.peltonen at helsinki.fi>

> 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
> --
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-- 
Dominique LALOT
Ingénieur Systèmes et Réseaux
http://annuaire.univmed.fr/showuser.php?uid=lalot