On 26 September 2001, Alexander <mlambrosa.it> wrote:
[...]
> Title: the best mode to deliver 1.000.000 email messages (recipient
> are ALL different and email are ALL different) in few hours during a
> single delivery session.
>
> You suppose to have a SMP Linux server (i.e. dual P-III 800 Mhz, 512
> MB Ram, SCSI Raid 5, kernel 2.4.9 and RaiserFS) and a good internet
> connection (4 Mbit/sec full bandwidth) and a fast DNS server near me.

    Wietse already explained how to setup Postfix for best performance.
Here's an additional checklist, mainly for the rest of the system:

- if possible, use OpenBSD or FreeBSD with softupdates rather than
  Linux;
- if you insist on using Linux, use a 2.2.x kernel, not a 2.4.x one, and
  turn OFF the swap; buy more RAM if you feel you're running out of it;
- use RAID 0+1, not 5, and (if you have that choice) mirror the stripes
  instead of striping the mirrors;
- use ext2; Xfs and Jfs are not yet ready for prime time, and everything
  else is slower than ext2 for mail handling;
- install a caching DNS on the SAME machine as the mail server, a nearby
  one is not good enough; use djbdns for that instead of bind; turn off
  logging for lookups, and give it plenty of memory to keep the cache;
- if you trust your UPS, turn off sync writes to the queue
  ("chattr -R -S /var/spool/postfix")
- if possible, send the logs to another machine instead of writing them
  to a local file, or at least put the logs on different disk spindles
  than the queue;
- apply Michael Tokarev's patch for CDB maps, and use CDB maps instead
  of hash.

(I'm sure I forgot a few things too.)

[...]
> Target: send 1 million of email in a very short time, shortest as
> possibile, it must end as soon as possibile. Bandwidth occupation is
> not a problem: we can use all 4 Mbit/sec (about 1 GB / 500 Kbytes/sec
> = about 2000 seconds , 1 hour and few minutes. 2 or 3 hours are ok
> anyway).
[...]

    As Wietse said, that's overly optimistic. With careful tuning,
Postfix would perform better than Exim and Qmail, but IMHO, no MTA would
be able to send 1 million messages in an hour, even over a LAN. No
offense intended, but people who set themselves such a target have never
managed a mail systems in the real world. For a today's PC, something
like 40-50 messages / second would still be an optimistic estimate;
that's about 6 times slower that what you want.

    Regards,

    Liviu Daia

-- 
Dr. Liviu Daia               e-mail:   Liviu.Daiaimar.ro
Institute of Mathematics     web page: http://www.imar.ro/~daia
of the Romanian Academy      PGP key:  http://www.imar.ro/~daia/daia.asc
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