[Dovecot] Running a dovecot cluster with mixed versions?

[Timo Sirainen]

On Fri, 2011-06-03 at 10:56 -0500, Ian Foutch wrote:
> I have been trying to find information and possible issues with
> running a cluster of dovecot server with different versions without
> any luck. 
> 
> We have an existing cluster with dovecot v1.1.10 and tried migrating
> to a new cluster with dovecot v2.0.12.  We ran into some issues when
> we moved traffic to the new cluster and have been unable to reproduce
> it in our own testing. We may need to put real usage on the new
> servers but would like to be able to do this by adding newer servers
> into the existing cluster. 
> 
> What are the potential issues with doing this?

Are they sharing mail files? It's similar to upgrading/downgrading then:
v2.0 can read index files created by v1.1, but once v2.0 has done
changes it's not a good idea for v1.1 to try to read the indexes
anymore.

Another possibility would have been to do this more gradually: First
upgrade to v1.2.17. There are no problems with v1.1.10 reading its index
files. After this upgrade to v2.0. v1.2.17 has no problems reading
v2.0's index files.