Planning for load balancing

[Ian Eiloart]

--On 19 November 2008 16:58:45 +0100 Jacco Rens <jacco at jaccorens.com> wrote:

> Hello,
>
> I'm currently running Apple's Mac OS X Server as mail server for about
> 100 users. The current setup has problem keeping up with all those
> users, since cyrus is limited to 300 sessions.

This is an operating system limitation, which you can change. In OSX 10.5, 
the hard coded system limit on processes is 2500, and you can set a 
sensible per user limit of, say, 2300. For 10.4 the hard coded limit is 
2068 (yes, really, not 2048).

To change the limits, create /etc/sysctl.conf, and insert these lines:

kern.maxproc=2500
kern.maxprocperuid=2300


> The mail client in use
> opens 4 sockets per account, so there are quite often time-outs or
> password errors during office time.

Actually, Apple Mail will open far more than 4 connections. It'll open one 
per mailbox. I don't understand this design choice - especially in the 
context of the server process limit above. Perhaps they just want to sell 
more servers.

> Now I want to look into solving
> this issue, without investing in new hardware. I can run VMware, with
> 2 or 3 more virtual Mac OS X Servers.

That's an interesting approach, but try increasing your process limits 
first. I've been supporting 12000 users on four physical hosts, but have 
just increased that to six.

> Would the cyrus murder function help me here?

It would, if you really need multiple hosts.

> Can anyone advice what could help?
>
> Best,
>
> 	Jar.
> ----
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-- 
Ian Eiloart
IT Services, University of Sussex
x3148