Re: Qmail/Postfix/Sendmail for fastest outgoing mail

[Craig Sanders <cas@taz.net.au>]

On Tue, Nov 26, 2002 at 12:00:32AM +1100, Craig Sanders wrote:
> > Actually, I can't see how Postfix would be at all faster, since it
> > would still be sending individual emails on separate connections. In
> > fact, wouldn't it be slower, since Qmail was optimized specifically
> > for this?
> 
> nope, because postfix is faster than qmail.  with some usage patterns
> (i.e. no VERP) it is much faster.  for others (e.g. VERP) is is only
> slightly faster.

actually, it's a lot better than i remembered it to be even when using
VERP.

postfix is between two and four times as fast as qmail with the same
load on the same hardware, depending on other, non-MTA, optimisations
(e.g.  filesystem tweaks).  the main reason for this is that postfix is
far more efficient in it's disk I/O.



http://www-dt.e-technik.uni-dortmund.de/~ma/postfix/vsqmail.html

in this benchmark, postfix delivered the same number of messages on
exactly the same hardware (running FreeBSD) about twice as fast as
qmail.  when you enable FreeBSD's filesystem softupdates (which is safe
to do with postfix, but not safe with qmail), the delivery speed almost
doubles again.

all the messages were to individual recipients, i.e. worst-case for
postfix.



there's a newer benchmark by the same guy with more details.  it
compares postfix, qmail, exim, and sendmail:

http://www-dt.e-technik.uni-dortmund.de/~ma/postfix/bench2.html


there are other MTA benchmarks around.  search on google if you want to
find more.


btw, on a linux box, use a better filesystem than ext2 or ext3 for best
performance.  XFS is good.  reiserfs is fine too.  with ext2/ext3 you
have to run 'chattr +S' on the spool directories to be safe, which makes
all write operations in that directory synchronous.  this is a real
performance killer.

craig

ps: i found a link to mini_sendmail, which looks like it may be exactly
what you need to replace the /usr/sbin/sendmail binary.

http://www.acme.com/software/mini_sendmail/

    mini_sendmail reads its standard input up to an end-of-file and
    sends a copy of the message found there to all of the addresses
    listed. The message is sent by connecting to a local SMTP
    server. This means mini_sendmail can be used to send email from
    inside a chroot(2) area.

-- 
craig sanders <cas@taz.net.au>

Fabricati Diem, PVNC.
 -- motto of the Ankh-Morpork City Watch