[Dovecot] cluster with dsync mirror

[Timo Sirainen]

On 16.8.2010, at 7.33, Bryan Vyhmeister wrote:

> Would it work to run 'dsync mirror' every minute against either mdbox
> or sdbox mailbox on a dedicated network connection between two (or
> potentially three or four) mail servers? I'm trying to avoid using a
> NAS/SAN or some other dedicated NFS server in a simple environment
> with a limited number of users. Everything else about the systems
> could be identical. Both could receive mail using Postfix with dovecot
> LDA. Thank you.

Were you thinking about master/slave or multi-master setup? Multi-master might work ok with director, as long as dsyncing is done often enough.

If you don't have many users, then maybe dsyncing once a minute is enough. A more optimal version would go something like:

 - create a dsyncing server process
 - create a Dovecot plugin (using notify plugin, similar to mail_log) that notifies dsyncing process every time some user's mailbox changes
 - based on that information, dsyncing process either runs dsync or delays it a bit. like maybe flag changes and expunges would be delayed a bit, but new mails would be immediately synced
 - run a full dsync for every user once in a while anyway, just in case some notifications were missed
 - implement a QRESYNC-like syncing for dsync to improve performance and reduce network traffic