[Dovecot] Dovecot strong or not for a big Webmail architecture

[Christian Balzer]

Hello,

On Thu, 2 Aug 2007 19:06:05 +0000 (GMT) John fistack
<john.fistack at yahoo.fr> wrote:
> 
> Do you think Dovecot could handle millions of active users in a big
> architecture ?
> 
Sure, but the architecture will play a bigger role than just
Dovecot.

> This cluster could be for example (each server is a bi quad Xeon 2.66
> Ghz) :
> - 40 Dovecot servers 
> - 4 LVS
> - 20 Apache+PHP
> - 2 Openldap
> - 20 Postfix + ClamAV + SpamAssassin
> - 1 NFS Netapps
> 
I'm not sure where you are pulling these numbers from (but then again
webmail is a lot more resource intensive than real mail clients).
We are handling about 100k users with a total of 9 machines and one
SAN backend. And yes, this includes all the components up there with
Exim instead of Postfix. About 10-20% are using webmail. 6 machines
are cluster pairs, 3 are MXs (no need for clustering there) and yes,
any single machine can fail and things will still work, pretty much
w/o noticeable performance impact, too. The whole thing is designed
to be pretty much indefinitely scalable.

For historical reasons we stayed clear of NFS (this system architecture
has been in production for 7 years, the last 3 with Dovecot), so I
can not comment on that part from own experience. But I have a hard
time imagining any single storage backend not melting from the traffic
that these amounts of machines would generate (if they are actually 
needed). And even if the backend could handle it, the network towards
it would be saturated a long time before those 40 Dovecot servers would
run out of steam CPU wise.

Regards,

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