Migrating from 2.0.x to 2.2

[Jens Dueholm Christensen]

Hi

I'm about to migrate a setup with <20 IMAP (but with a few million mails in all) accounts that belong to the same system-user on an older machine running Dovecot 2.0.13 to a new machine running Dovecot 2.2.13 (or possibly newer..).

Mails are stored in Maildirs with no special or advanced features (like alternate storage etc etc).
Filesystems are prepared for the expected amount of inodes required, and for the time beeing a change to mdbox is seen as an added complexity.

One requirement of the migration is that messageID is not changed - mails are referenced by other systems that expect to find individual mails by the ID.

Since dsync is incompatible between 2.0<->2.1<->2.2 what is the best way to perform this migration?

I was hoping of rsync'ing all Maildirs from the old machine to the new one (including indexes etc etc) and power up Dovecot 2.2.x and see what happens, but is that possible or is there another (and better) way short of installing 2.0.x on the new machine, rsync everything and then upgrade to 2.2.x?

Regards,
Jens Dueholm Christensen