Storing incoming work dir on ramdisk

[Julian Field]

At 20:37 01/01/2003, you wrote:
>On Wed, 1 Jan 2003, Julian Field wrote:
> > 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
>
>Those are pretty impressive numbers!  I noticed that you're testing with
>Exim instead of sendmail.  Do you think there would be much difference if
>you used sendmail?

Sorry for the delay, I have been pumping a few hundred thousand email
messages through my server to find the timings.

Sendmail is working a *lot* slower than Exim.

All outgoing mail is pumped to a dual-CPU 1GHz P3 machine which is running
a very simple SMTP "sink" that throws away everything it is sent, but
speaks just enough SMTP to make the clients think they are talking to a
real SMTP server.

With sendmail, the stats are these:
Sendmail, all directories on disk, 387300 per day.
Sendmail, incoming+quarantine on tmpfs, 10:18:29-11:23:21, 444000 per day.
Sendmail, all on tmpfs, 453000 per day.

So with sendmail it isn't worth the bother as the overhead of just sending
the SMTP traffic is so high. Interesting that Exim manages to do the same
job in about 1/3 of the time!
--
Julian Field
www.MailScanner.info
MailScanner thanks transtec Computers for their support