upgrade from 2.0 to 2.2

[tetlika]

hi!

according to the doc: http://docs.mongodb.org/manual/release-notes/2.2/
: "Balancing is not currently supported in mixed 2.0.x and 2.2.0
deployments. Thus you will want to reach a consistent version for all
shards within a reasonable period of time, e.g. same-day. See
SERVER-6902 for more information."

but what about such case: can I have hidden secondaries with priority
0 in sharded cluster with version 2.2 while all other members will be
with 2.0 + balancing enabled?

[tetlika]

[tetlika]

anyone?

[Spencer T Brody]

Yes, that should work.  So long as the primaries for all replica sets are always the same version balancing should continue to work.

[William Zola]

While possible, this configuration is inadvisable for a variety of reasons.

You really, really, really want to have all of the nodes in your cluster running the exact same minor versions.  Any attempts to get "clever" and mix versions will eventually come back and cause you pain.

 -William 

[tetlika]

I'm going to do that because I have reasons to upgrade my cluster in
such a way:

1) add v2.2 hidden secondaries with priority 0 and sync data from
scratch on each shard , than make a snapshots of synced data from
them
2) stop balancing
3) upgrade all mongoses
4) upgrade configs one by one
5) restore non-zero priority secondaries from snapshots taken on step1
and run 2.2.3 on them
6) stepdown 2.0 primaries
7) remove hidden secondaries
8) upgrade 2.0 secondaries (those which were masters)
9) enable balancing