[Mailman-Developers] VERPing: ouch!

[J C Lawrence]

On Tue, 13 Jul 2004 14:28:34 +0200 
fil  <fil at rezo.net> wrote:

>> I ask because Chuq Von Rospach has done some calculations on what
>> should theoretically happen to your performance if you enable VERP,
>> but I don't know of anyone who has actually timed the performance
>> difference on large lists.

> Usually the sending (mailman to postfix to 90% of users) takes a bit
> more than two hours ; yesterday it took about 6 hours. 

That's an effective delivery rate of ~1,300 deliveries per minute, which
is fairly low assuming moderate hardware.  

  ObNote: I found I could sustain 2,400 deliveries per minute with a
  quick-poke tuned Postfix on a 512Meg RAM PII-333 with separate
  spindles for spool and log.  Some minor efforts at more disciplined
  tuning suggested that it could sustain 2,800+, but I could never
  verify that as I just couldn't keep the spool fed fast enough.

> But more importantly, the Mailman -> postfix thing took 5 hours
> instead of ~ 15 minutes.

What system metrics spiked during this time?  160K/5 hours is a delivery
rate of less than 600 per minute.  That's one message every 10+ seconds
which is quite slow.  Even if you double that (receipt and transmission)
that's only 1,200 per minute which is still dawdling territory.  Your
MTA should have been able to keep that spool empty while twiddling its
thumbs.

-- 
J C Lawrence
---------(*)                Satan, oscillate my metallic sonatas.
claw at kanga.nu               He lived as a devil, eh?
http://www.kanga.nu/~claw/  Evil is a name of a foeman, as I live.