Storing incoming work dir on ramdisk

[Julian Field]

I've just done an experiment on my biggest server (thankyou Transtec!).

I am ignoring incoming SMTP traffic load for now, as I have yet to find
enough machines to feed it SMTP traffic at 1.5 million messages per day.

Using disk-based directories for
        mqueue.in
        mqueue
        MailScanner/incoming
        using Exim
I can process about 1.1 million messages per day, using Sophos,
SpamAssassin and the default RBL lists.

With tmpfs-based directories for
        MailScanner/incoming
this jumps to about 1.4 million messages per day, using the same settings.
This is perfectly safe as the MailScanner/incoming directory is wiped at
startup anyway, and no messages can be lost by power-outs.

With tmpfs-based directories for
        mqueue.in
        mqueue
        MailScanner/incoming
this increases to about 1.5 million messages per day, using the same
settings. This is not safe as the mqueue.in and.mqueue would be lost on
power-outs.

So if you have the RAM to throw at it, and plenty of CPU horse-power to
make use of it, you can increase your message throughput by roughly 30% by
moving the MailScanner/incoming directory onto a tmpfs filesystem held in RAM.

But if you run out of RAM and start swapping a lot, the performance will
drop quickly.

Tests done on a Transtec 2600 Workgroup Server, 2 x 2.4GHz/Zeon with 2Gb
RAM, 15000rpm SCSI disk, 15 child processes.
--
Julian Field
www.MailScanner.info
MailScanner thanks transtec Computers for their support