[imp] Help Req. : Sizing a Horde\IMP system for 12,000 users

[Christopher Crowley]

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> 2) You'll be able to handle more concurrent users if you're using 
> php-accelerator from http://phpaccelerator.co.uk/ .  It's free and 
> seriously speeds up php access for IMP.  It hasn't yet been ported
> to  Solaris 9 directly, but you might try it as is, or volunteer
> hardware for  the author to port it on.

I think it works on Solaris 9. I have it running on a test Solaris 9
box, and on the production Solaris 8 installation, where it made a
huge improvement.  But I haven't load tested on the Solaris 9 server.

My cache is usually about 6.5 Mb, the entire horde directory at my
install is about 10 Mb.  The Apache server basically does not go to
disk.

> >clue how many are logged in at a given time.  (Side topic: does
> >anyone know an easy way to track the number of currently logged in
> >users?)  

I would like to know this, too. I have tried counting the number of
active (non-stale) files in the /tmp/session directory where session
files are stored.  If you are using MySQL to manage sessions, you
could do a DB query.

> >During the peak times of the day, we get about 35 hits per second
> >on each of our two webmail servers.
> >

Tulane's IMP installation receives about 6,000 unique logons per day.
 MySQL and Apache webmail are on an E-450 with 4GB ram and 4 CPUs. 
The RAM was necesary.  We also have a SSL accelerator (SonicWall)
which handles all the SSL/TLS transactions.  The site is entirely
SSL.  We are poised with a load-balanced solution, which we will
implement when the web server demand reaches a critical state.  The
php-accelerator was enough to make it that we didn't have to go to
the load balanced scenario quite yet.

Our current bottleneck is the (IMAP) e-mail server.  Even with very
fast disk (Xiotech SAN) for inbox and IMAP folders, the server still 
suffers from CPU constraints.  I tried IMAPproxy (tonight) and it was
working quite well until it hung.  I hope to work through those
issues, and replace the tremendous number of IMAP logins with
persistent connections. (Anyone with large Solaris 8 IMAPproxy
implementations, please e-mail with tips / trouble shooting
assistance.)

I have posted this config information previously( check in the Marc
archive ).  There have been a few other relevant inquiries, and other
more impressive, and/or more efficient scenarios have been explained.
 We are departing from the monolithic paradigm and entering the
load-balanced / load-shared paradigm. I suggest you design your large
implementation with that in mind.  

Hope it helps.

Christopher Crowley
TIS Network Services
Tulane University
ccrowley@tulane.edu
504.314.2535
PGP Key ID: 0x7CF18FDB




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