[Linux-cluster] Re: E-Mail Cluster

[Jan-Frode Myklebust]

On 2006-07-31, Nicholas Anderson <nicholas at fiocruz.br> wrote:

> I'm new to clustering and was wondering what would be the best solution 
> when clustering an email server.
>
> Today we've 1 server  with a storage where all mailboxes (mbox format) 

For clustering, I think it would be better to use Maildir-format
for the mailboxes. Then you'll avoid any locking problems on the
mailboxes. New messages can be delivered on one machine while other
messages in the same mail-folder is being deleted on another machine.

If your users are only accessing their email by pop/imap, moving to 
Maildir shouldn't be any issue.

> and home dirs are stored.
> I'm planning to use 3 or 4 nodes running imap, pop and smtp, all of them 
> sharing users' data.
>
> Should I use NFS or GFS?

NFS is very single-point-of-failure.. so definately a clusterfs/GFS.
If you can move to Maildir, you should be able to run any number of
servers where each server is running all services (imap, pop and smtp), 
and incoming traffic is routed to a random server trough f.ex. round
robin dns.

To handle single-node downtime/crash, you'll just need to move the
ip-address to an available node. Easily achivable trough f.ex. 
heartbeat from linux-ha.org, and probably also RH Cluster Suite..


  -jf