On Jul 24, 2009, at 5:00 AM, Joseba Torre wrote:
we have a medium setup (8000 pop and imap users using almost every
available client, 800GB of stored mails using maildir on a Celerra NFS
server, with index files on local disks, and procmail for local
delivery), being served by a Dell PowerEdge 2850 (2GB RAM and dual P4
Xeon 3,2GHz).
Our current not-so-high availability setup is based on a similar
server with the same setup and a easy but manual process to switch
from one server to another.
So you currenly have a single server serving all imap/pop3 users?
- The recommended setup, with each user being sent always to the same
server, is not possible because our load balancers (Cisco Catalyst
6000) can't do that.
- We could put both servers behind the load balancer, and keep local
index files on each server. Usually the same ip we'll be redirected to
the same server, so few problems will arise. When a user is sent to a
new server, index will be rebuilt so performance will be bad but we
should not expect other problems, right?
If a single server can handle all users fine, I wouldn't try anything
special here. Just have them work as a master/slave and install some
kind of a heartbeat to switch between them.
- We could also put the index files on a nfs share. No problems, but
pretty bad performance.
If there's only a single server accessing the mails, you can use
mail_nfs_*=no and the performance shouldn't be that bad.
- We could also get more ram for the servers and keep indices in
memory.
I'd say local disk is much better.
Using deliver instead of procmail could improve performance?
http://wiki.dovecot.org/LDA/Indexing
- We've also thought about some more or less weird setups, like
setting up a GFS filesystem for the index files, or setting up a proxy
on every server which redirect users to their fixed server, but they
seem too complex for few advantages.
Assuming still a master/slave setup, you could use DRBD to replicate
indexes between local disks.
