[Mimedefang] MD I/O intensive?

[David F. Skoll]

On Mon, 15 Mar 2004, Aaron Paetznick wrote:

> I'm assembling several front-end MIMEDefang filter servers.  These
> machines will be used to filter incoming email and pass it along to our
> mailstore.  They will be under extremely heavy load.  I'm wondering how
> I/O intensive the Sendmail/MIMEDefang combination is in a setup like
> this.  I would also be using File::Scan and clamd.

You must, must, _must_, use a ramdisk for the /var/spool/MIMEDefang
directory.

Did I mention that you need to use a ramdisk for /var/spool/MIMEDefang?

If you do that, then the I/O load is approximately the same as for
normal Sendmail.  Ideally, you want /var/spool/mqueue to be on a dedicated,
fast drive.  You also want to configure syslog not to flush to disk after
each log message.  In Linux, you do that by prefixing the output file
name in /etc/syslog.conf with "-".

> When used in this configuration, will CPU, memory, or I/O be the
> bottleneck?

Yes.

Seriously, it depends on the e-mail pattern.  Memory pressure is usually
quite high on busy machines; you want lots of RAM.  Once you have enough
memory, CPU and I/O pretty much fight it out evenly for the honor of
being the bottleneck (at least on a well-configured machine.)

Regards,

David.