dovecot - Jun 2011 - Running a dovecot cluster with mixed versions?

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?

Thanks,
--Ian



 
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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.