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

[Shawn Robinson]

At 10:24 AM 2002/12/09 -0700, you wrote:
>On Mon, 9 Dec 2002, Martin Searle wrote:
>
> > Hi,
> >
> > I work for the University of Kent in the UK and we are looking to
> > replace our current Email client with a horde\IMP webmail system. I
> > have been asked to research what sort of machine(s) is required to run
> > the system, it maybe that a clustered approach would be better ?.
> >
> > Our current Horde IMP system shows excessive strain with about 2-3,000
> > users logged in its a Sun Blade 100, 384mb, 9gb disk machine, which
> > granted is not a very powerful piece of kit, it runs IMP v2.2.6. We
> > have apache and Solaris 9 on the machine. This machine serves
> > off-campus users mainly although some internal users have switched to
> > it exclusively.

I'd guess you'd start swapping before you run out of CPU. Each instance of 
Apache/PHP /PHPAccelerator takes about 10MB resident, and the imap c-client 
likes to allocate memory ;)  We run multiple Netra AC200's with 1GB RAM 
behind F5 load balancers in an ISP environment.

Your best bet is to separate out the functions as Eric Rostetter suggested.
1) put your IMAP servers on one or more separate boxes, and have dedicated 
hardware for IMP.
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.
3) Use SMTP to send messages instead of sendmail.  It's faster and you 
don't have to manage local queues.
4) Don't let people use POP3. :)
5) The database requirements are pretty low (we run a dedicated AC200 for 
mysql with a standby) and have about 1 million address book entries, half a 
million preference settings, and around 200K active user entries.  The disk 
IO is spread across a software mirror.  We added an additional index on the 
addressbook entries on the owner attribute as mentioned in the list archives.

Regards,
Shawn


> >
> > Our current email system handles approx. 60,000 outgoing emails per
> > day from a variety of clients.
> >
> > We do have a limited budget and we would like to continue to use Sun
> > hardware. So does anyone have any thoughts or have first hand
> > experience with setting up a system to handle more than 10,000
> > concurrent users ? My gut reaction is too look at clustering and use
> > spare space on existing servers.
>
>You don't really say what you mean by 10,000 concurrent users...  Our
>webmail system handles about 13,000 logins per day, but I don't have a
>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?)
>During the peak times of the day, we get about 35 hits per second on each
>of our two webmail servers.
>
>The two servers are Dell 2650s with dual P4 2.2GHz cpus, 1GB RAM, and two
>18GB drives (mirrored) running Debian Linux 3.0 (Woody!).  We run Horde
>2.1, IMP 3.1, Turba 1.1, and Kronolith 1.0.  A separate database server is
>used for preferences and session storage.  The two webmail servers sit
>behind a Foundry Networks ServerIronXL load balancer.  With our current
>load, we could probably operate with only one of these webmail servers
>running, but we planned for growth.
>
>         Andy
>
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