So the question is, if I stage the upgrade, will it break replication between the two backend storage servers?  My thought was to upgrade one to 2.3, and keep the other on 2.2 for a couple of days?  If so, can 2.2 replicate to 2.3, and 2.3 replicate to 2.2 without any issue?  Or am I going to have to go all-in on 2.3 at once on both? Heh.