[Dovecot] migration from dovecot to dovecot on different servers without downtime (dovecot replication?)

[Pau Oliva]

Hello,

I have an imap server with huge Maildirs and several users running 
dovecot 1.0.13, I need to migrate all the imap accounts to a new box 
which runs dovecot 1.1.4.

The requisite is that need to do it with no downtime or minimal downtime 
possible, and totally transparent for end users.

I have tried IMAP<-->IMAP syncing using a master user in both servers 
and imapsync, however due to the huge Maildirs (some users have more 
than 10 years of mail) this tends to be quite slow and painful.

Can I tar all the user's Maildir and move them from one box to the 
other, and then run imapsync again? which I assume that would be 
faster... or is there any better solution I am not aware of? (ie: I've 
seen some emails about dovecot replication on the list archives, but few 
details of how that should be configured).

I'd appreciate any feedback or thoughts on this matter. Thank you.

Cheers,

	Pau Oliva