[Dovecot] 1.0.15 -> 2.x upgrade for mass hosting environment

[Timo Sirainen]

On 1.3.2011, at 18.57, lists at truthisfreedom.org.uk wrote:

> Quoting Ed W <lists at wildgooses.com>:
>> Hi, don't have an installation of anything approaching your size.
>> However, I do regularly see folks missing out on the idea that its
>> reasonably straightforward to have both Dovecot (old) and Dovecot (new)
>> versions running at the same time and migrate users over slowly rather
>> than in a big bang?
> 
> Yeah, we're actually now thinking that we should create a new cluster running dovecot 2.0, mount the existing control/maildir files from the current shared storage and then regenerate the indices before going live - would that work here? I'm struggling to find anything in the docs that state the control files will be affected by the upgrade.

v2.0 will read v1.x indexes just fine, no need to do any regeneration. (But v2.0 indexes can be read only by v1.2.5+.)