Patrick Chemla:
> Wietse,
> >> Please try the following, as asked half a week ago:
> >>
> >> postconf -e smtp_connection_cache_on_demand=no
> >> postfix reload
> >>
> >> and report if this makes a difference.
> >> Wietse
> >>
> I have tested this since yesterday night.
>
> I got some problems with Linux per user number of processes limit. I
> fixed it. I also increased some delivery concurrency figures, and now I
> can see up to 1300 processes delivering emails to the qmail servers.
>
> I had a few minutes shot today at a rate of 6300 emails per minute. I
> ran a full hour at 180,000 emails per hour. The outbound line was saturated.
>
> CPU is about 30% loaded, no Wait I/O, no swap, memory is large.
>
> I think I will reach about 600,000 emails per hour if I fix some timeout
> on the qmails (replace by postfix?). Maybe I could reach 1 million?
OK, so you can turn back on that connection caching. Note that
qmail creates and destroys two processes per SMTP session, so
reusing a session is also a win from a CPU resource point of view.
1M/hour, or less than 300/s, should be possible (you mention the
queue is on a solid-state disk). Barring brain damage such as
synchronous syslogging by default on some Linux boxes, borked DNS,
process/file/etc. resource limits, etc.
Perhaps this is a good time to mention that SecurityFocus was
ezmlm->qmail based, and that they switched to Postfix for outbound
deliveries, because qmail simply could not keep up with the volume:
inbound mail -> qmail -> ezmlm -> multiple postfix MTAs -> internet
That was 2001 when I added QMQP support to Postfix, and this is
still what they appear to be using now, if I must believe their
own Received: message headers.
Received: from lists2.securityfocus.com (lists2.securityfocus.com
[205.206.231.20])
by outgoing2.securityfocus.com (Postfix) with QMQP
id 8AC0814370A; Thu, 7 Jan 2010 14:11:35 -0700 (MST)
My very first qmail/Postfix benchmarks showed that qmail was up to
three times slower as a transit MTA, simply because qmail creates
three queue files where Postfix creates one. Creating/deleting
files involves more disk access operations than reading/writing
files, and that hurts especially with small email messages.
Wietse
