[Dovecot] quota calculating

[Christian Balzer]

Hello,

On Mon, 25 Jun 2007 10:10:00 -0400 (EDT) "Scott Zahn" <scott at zahna.com>
wrote:
>      Currently where I work we use qmail.  

My condolences. The worlds most patched PoS (software, really, I
mean software) by the biggest ego in the business. 

> Every time a message is
> delivered, qmail seems to walk through the user's entire maildir in
> order to calculate quota usage.  

That doesn't seem right, not if it is using maildirsize maildir++
quotas, see:
http://www.inter7.com/courierimap/README.maildirquota.html

The worst case scenario would be a full mailbox, which would trigger
a full recalculation every 15 minutes (Exim does it every 20 minutes).
This recalculation is part of the specification, of course a smartly
designed mail system will (with a few scripts and a database of sorts)
prevent delivery attempts (and thus recalcs) to full mailboxes.

So the first thing to check is if these mailboxes are perma-full
or if they get so much activity that the maildirsize quickly grows
to the 5k size that triggers a recalculation. If neither is the
case, then yes, qmail is your enemy (surprise, surprise).
Or if you are delivering with something else, that is the culprit then.

> Delivering messages simultaneously to
> just a few users who are allowed large maildirs (1-2GB) will bring our
> servers to their knees.  Which brings me to dovecot.  I use dovecot
> whereever I can, but haven't yet needed to set up quotas.  I would like
> to migrate my servers at work to use dovecot, but have a few questions
> regarding quotas.  Could someone explain how dovecot calculates quota
> usage on mail delivery?  Also, is there anyone here on the list that
> uses quoatas on large maildirs (>=2GB)?  How well has it worked for you?
> 
Again, having to recalculate the quota eventually is part of the 
specification. If your hardware (I/O) can stand the infrequent 
recalculations working maildir++ quota requires you are gold. 

Regards,

Christian
-- 
Christian Balzer        Network/Systems Engineer                NOC
chibi at gol.com   	Global OnLine Japan/Fusion Network Services
http://www.gol.com/