upgrading a 2.2.12 murder to 2.3.14

[Andrew Morgan]

On Thu, 16 Jul 2009, Gavin Gray wrote:

> We are planning towards upgrading our existing murder. The murder has
> four front ends, three backends and separate mupdate and lmtp servers.
> We want to move from version 2.2.12 to 2.3.14 so that we can make use
> of delayed expunge an possible replication.
>
> We have several thousand users currently having 4 TB of mail.
>
> Any comments on the following would be welcome:
>
> 1. We plan to gradually migrate users from the existing backend
> machines to new backend servers running 2.3.14 that have been
> integrated into our murder. We plan to do this using xfer. Although
> this is very time consuming we are under the impression that cyrus
> recommends using imap itself to do migrations rather than trying
> underlying filesystem copies of some kind.
>
> 2. We should end up then with our existing murder but with three
> backends running 2.3.14. We then plan to upgrade the other machines in
> the murder to 2.3.14 in the following order: frontends then lmtp and
> finally the mupdate server. Does this make sense?

Whatever you do, don't upgrade any of your frontends while you have older 
backends.  The 2.3 code uses new IMAP calls that don't exist in 2.2. 
Quoting myself from a couple years ago:

   I proceeded assuming I could have a v2.3.10 frontend with older v2.2.13
   backends.  However, I was unable to get the APPEND command to work.
   With telemetry logging enabled, I discovered that a 2.3 frontend issues
   the IMAP command "Localappend" to a backend.  However, my v2.2.13
   backend does not recognize "Localappend" as a valid command (and it is
   not present in the source code).

 	Andy