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Subject: RE: Performance ....
From: Mark Hoffman (mark.hoffmanwallst.com)
Date: Thu Jun 29 2000 - 11:29:31 CDT

I'm delivering 250k distinct emails per day. 90% in less than 2 hours. I've
used Qmail for this, but now use Postfix exclusively.

One thing I found with Qmail is that if you are streaming mail to it very
quickly, once the active queue gets to be over 100 or so, it stops spawning
new delivery threads. This causes a slowdown in general. It will queue up
mail forever, if you want. If the emails are time-critical, Postfix is much
better, because Postfix will slow down the queueing process while still
delivering at peak capacity. The bottleneck we've run into with Postfix
isn't a Postfix problem. It's writing the queued mail to disk. Even after
tweaking the OS (BSD/OS 4.1), we still cannot get emails to disk fast
enough. The benefit of Postfix is that it will slow down responses to the
clients when this happens, so you know when things are backing up on the
client end.

Qmail is great for mailing lists, what it was written for. Postfix is better
for lots of discrete emails.

Mark

-----Original Message-----
From: Bennett Todd [mailto:betrahul.net]
Sent: Wednesday, June 28, 2000 3:38 PM
To: Laughton, Brian
Cc: 'postfix-userspostfix.org'
Subject: Re: Performance ....

2000-06-28-15:18:27 Laughton, Brian:
> We are looking at migrating from sendmail to either postfix or
> qmail. Does anybody have any documents regarding the performance
> capabilities of the two pieces of softwae ???? (IE which is
> faster)

Both postfix and qmail should be so breathtakingly much faster than
sendmail, both for individual messages and in aggregate delivery
rates, that any difference between them should be imperceptible by
comparison.

I've heard it suggested that Postfix may, possibly, be a bit quicker
than qmail in some settings, because it does one fewer file I/O or
something in the critical path of handling a message.

But I think most serious MTA advocates would agree that the
performance difference between Postfix and qmail simply doesn't
qualify as an important difference. Choose between them based on
style. Try each one, see which one you like best. Either should
serve you very well.

Personally, I happen to like Postfix better; it's configuration
style (nearly all variables in one file), it's focus on
drop-in-compat with sendmail, and Wietse's willingness to change
Postfix to meet peoples' needs all work better for me than the
corresponding attributes with qmail.

-Bennett