Storing incoming work dir on ramdisk

Julian Field mailscanner at
Wed Jan 1 19:53:28 GMT 2003

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
        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
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
this increases to about 1.5 million messages per day, using the same
settings. This is not safe as the and.mqueue would be lost on

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
MailScanner thanks transtec Computers for their support

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