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Re: Mail server

----- Original Message -----
From: "Russell Coker" <russell@coker.com.au>
To: "Colin Ellis" <colin@solution-city.com>; <debian-user@lists.debian.org>
Cc: <debian-isp@lists.debian.org>
Sent: Monday, February 24, 2003 7:16 PM
Subject: Re: Mail server
> If a message delivery takes 10 disk writes (actually it probably takes
> once you count writing to two files in the queue then writing it to the
> and deleting the queue files with lots of fsync() along the way) then such
> machine can only deliver 13 messages per second.
> I'm running a number of mail servers with lots of spare disk space that
> hitting the message delivery limits, which prevents me adding more users.

I totally agree with Russel; disk speed is probably the most important
limiting factor, not CPU speed or diskspace.

To add some more numbers: I've just been doing some benchmarks to test
different filesystem/mailserver combinations, testing with Russel's
excellent Postal benchmark program.
The best result on our testmachine (celeron 1700, 256 megs of RAM, 80  GB
7200 rpm IDE disk) have been a constant 30-35 messages per second. This was
with a combination of XFS, Exim and Maildir storage, and with a maximum
message size of 10K. A more realistic 100K maximum size still resulted in
about 20-25 deliveries per second.

These numbers are, however, only for mail delivery using SMTP; retrieving
the mail using either POP or IMAP will add significant load.

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