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Subject: Re: Relaying Performance
From: Wietse Venema (wietseporcupine.org)
Date: Sun Feb 06 2000 - 05:02:18 CST

Gregory Stark:
> To switch we would need postfix to accept mail over a handful of connections,
> or ideally a single connection, at a rate of at least 20/s, preferably over
> 100/s. Then be able to keep up delivering all the mail as fast as it's
> received.
>
> Our initial experiments seemed to indicate that it couldn't deliver faster
> than about 5/s. Is this just a simple tuning issue or are the numbers I'm
> talking about simply infeasible with postfix?

Postfix has a weak spot here where a lot of inbound mail can swamp
all the I/O resources so that delivery rates drop. You can quite
likely get more mail through Postfix by reducing the number of SMTP
server processes.

This is an old problem. Only recently have I have figured out a
more reasonable solution that can prevent this scenario from
happening. In a nutshell, it introduces a stiffer coupling between
the receiving side and the delivering side. I hope to implement
this solution shortly.

With monolithic mailers like sendmail and exim you get the stiffer
coupling for free, with broken-up mailers like Postfix or qmail
some extra work needs to be done.

        Wietse