[Dovecot] Hints for a NFS-Setup

[Nick Warr]

Il 30/03/2012 13.31, Patrick Westenberg ha scritto:
> Hi everyone,
>
> as I have often trouble with OCFS2 I want to switch to NFS but
> I'm not sure how to rebuild my cluster with regard to locking
> and indexing problems.
>
> By now my I have a four server configuration (there are another 2
> servers for outgoing mail but they can be ignored):
>
> MTA(MX10) --(lmtp/socket)--> local dovecot --> iSCSI-LUN with OCFS2
> MTA(MX10) --(lmtp/socket)--> local dovecot --> iSCSI-LUN with OCFS2
> IMAP-User <--(imap)--> IMAP-Server1 (local dovecot) <--> iSCSI-LUN/OCFS2
> IMAP-User <--(imap)--> IMAP-Server2 (local dovecot) <--> iSCSI-LUN/OCFS2
>
> As far as I understood I will get poor performance if I'd just switch
> from OCFS2 to NFS (while keeping this configuration) with 4 hosts
> accessing the NFS-share and the index files on it and it is recommended
> to assign users to a specific host (http://wiki2.dovecot.org/NFS).
>
> I'm uncertain what's the meaning of "user" in this context. Is it an
> IMAP-User or every incoming mail?
>
> An IMAP-User assigned to a specific IMAP-Server is ok for me and I
> could store and profit from local index files. However, I want my
> incoming mailservers to be equally receiving mails. Both should accept
> mails for every mailbox but in this case I won't have local indexes.
>
> I would appreciate any hints.
>
> Patrick
If you've got a load balancer, it should be fairly easy to do simple IP 
stickiness, with a long enough timeout, most IMAP and POP3 users will 
stay on the same server.. I'm sure there is some load balancing software 
that's also L7 aware, and could direct by username (though you'd 
probably have to have the LB terminate the SSL, not the server behind it).

SMTP wouldn't have to be balanced in the same way, you could just use 
round robin in that case..

I think some of the new Dovecot (director?) software is user aware, but 
I don't know if it's quite ready for production.