Re: Qmail on lists.debian.org is costing me real money
On Mon, 16 Mar 1998, Ian Jackson wrote:
> The fact that lists.debian.org runs qmail is costing me real money:
Having mulple users subscribed to the same list on the same machine is the
major case where qmail is bandwidth inefficient, but this is fairly rare
on our lists.
Here is why the list server (murphy) runs qmail,
- It is very low overhead and -extremely- effecient for the single case
when it is performing deliveries to a large number of addresses with
minimal host overlap. This means a mailer like exim will be doing
extra useless work trying to sort the address list of 400 by mx.
- It is very, fast. With 120 parallel deliveries an email accepted to
the list server will distribute to 90% of the addresses in under
1 minuite, there is no lag.
It's downsides are
- Not DFSG
- Will not, in an case, send more than one email over a smtp connection.
> All of us could each run a local exploder, but this is a lot of hassle
> when individual local people want to (un)subscribe. Wouldn't it be
> better if lists ran a more efficient and DFSG-free MTA such as Exim ?
I would like to see proof that exim can handle the same delivery rate as
qmail does before even considering it, I do not belive it will. Right now
the best candidate for the list server is zmailer but it is rumored to be
very hard to configure. Exim would be runable on the other two machines
but that would mean rewriting every single .qmail file.
Just for the record, yesterdays qmail log file for the list server was 50
megs. A grep reports the machine did 186000 successfull deliveries (both
local and remote) and had 46640 deferrals. During the same time period it
accepted 2000 smtp connections. The list log shows that 5megs of input
list mail have happened since we moved to va. By my estimate that is a
sustained delivery rate of 0.3msg/sec. Now, qmail peaks at over 20msgs/sec
when delivering the list mail (biggest list is 400 subscribers so it would
take 20s if all the hosts were fast), murphy will peak even higher as I
have raised the limits to allow 240 concurrant remote deliveries. Any
mailer which cannot handle >100 concurrante remote deliveries or cannot
handle that sort of message volume is simply not acceptable. BTW - while
doing this the load on the machine is typically 2-3 for about a min (the
PPro200 rarely goes above 1, this was the P90), then drops to less. The
reason master got so high is because CVS caused the machine to run out of
ram which caused qmail to swap which drove the load into the high 40's.
The above number were only for va, master which handles the user accounts
is also a 4 meg log file, it reports 12000 sucessfull deliveries and 1287
deferalls, it accepted 2000 smtp connections.
Jason
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