2016-10-24 14:47 GMT+02:00 Michael Seevogel <ms@ddnetservice.de>:
If your server OS supports newer Dovecot versions then I would highly suggest you to upgrade to Dovecot 2.2.xx (or at least to the latest 2.1) and set up Dovecot's replication[1] feature.
Are you talking about the new server or the older one that I have to replace? The new server has to be installed from scratch, so, yes, I can use Dovecot 2.2 from Jessie
The "old" server is based on Squeeze, I can upgrade that to Wheezy and install Dovecot 2.2 from wheezy-backports but I have huge trouble when I've tried to do the same on a similiar server. I was unable to upgrade the dovecot configuration by following the documentation as this didn't work:
doveconf -n -c /etc/dovecot/dovecot.conf > dovecot-2.conf
I had an empty dovecot-2.conf file, no warning or output at all. It did nothing.
With this method you can actually archieve a smooth migration while your current server replicates all emails in real time to your new server, including new incoming emails and also mailbox changes to your new server and when the migration is done you'll just have to change your DNS and disable the Replication service.
Cool. Any guide about this ? Should I start the replication on one side and wait for finish before pointing the mailbox to the new server?
If you don't want or cannot set up replication you could still do a one-shot migration via Dovecot's dsync[2] on the new server, pulling the mails from the old. 50GB isn't that much as long as your two servers are at least connected with 100 Mbit to the inet. You may want to block for the time of the migration via iptables your users accessing Dovecot. However, under the bottom-line, if this is really necessary depends on you and the needs of your mailusers/customers.
I can't block the whole server. I have to migrate 1 user at once. But I can disable the pop3/imap access for that user, so noone is changing the files during the migration (except for the postfix/exim delivery agent)
P.S. You should think about to use on the new server mdbox as mailbox format. That's kinda a hybrid of mbox and maildir and benefits of features of both its predecessors. However, backup and restoring is in case of mdbox "a bit" different. Just have a read...
[1] http://wiki.dovecot.org/Replication [2] http://wiki2.dovecot.org/Migration/Dsync
Thank you