[Dovecot] problems with SSH-based clustering dovecot 2.1.1

[Timo Sirainen]

On Wed, 2012-03-14 at 01:25 -0400, Michescu Andrei wrote:
> Now, as long as I touch the mailbox of user1 only on mx1.a doveadm sync
> keeps them in sync (cron job every 5 minutes).
> 
> The problem comes when I start using the master-master model: emails
> starts getting duplicate with different ids.

I was testing this a bit, and I guess in your tests dsync was running
during a mail delivery, which seems to make it duplicate mails
sometimes. I'll probably fix this at some point (I've actually been
thinking about a larger dsync redesign), but anyway:

Even if dsync worked perfectly and didn't duplicate mails, it's not a
great idea to do deliver mails randomly to both servers. Each time dsync
notices that both sides have had new mails, it needs to reassign new
IMAP UIDs for the messages, which means that IMAP clients may need to
redownload the mails. Better to give one MX a higher priority so mails
typically are delivered through it.