dovecot - Oct 2013 - Questio about replication

Hi everyone,

this article 
(http://blog.dovecot.org/2012/02/dovecot-clustering-with-dsync-based.html) 
describes the situation for director/NFS-based clusters and SSH-based 
clusters.

Right now I'm running the first setup with one proxy/director and two 
backends (all 2.2.x) mounting an NFS-share but I'd like to get rid of
NFS (it's slow) and, if one backend is down, the proxy still sends the 
user to that backend.

The article says:
"High-availability non-NFS setup
One possibility is to use Dovecot proxies, which know which servers are 
down. Instead of directing users to those servers, it would direct them 
to replica servers."

My question is, if I can still use my proxy/direcot setup but every 
backend having it's local (or iSCSI-backed) ext4 storage and not using 
the SSH-based replication method?

Regards
Patrick

Hi Patrick,

You can use the proxy in combination with a database to return a fixed backend
host per user, but be aware of the fact that if one host goes down, all
mailboxes on this host will also be down (if there is no replica).

The director uses a hash function instead and can only be used when all backend
nodes can serve the same set of users. The director uses the proxy feature to
forward the connection to the backend host, but the backend is selected by the
hash function depending on the username.

In short: use the proxy not the director, but keep copies/replica of your
mailboxes somewhere in case one host goes down.

Regards
Daniel