@olivierlambert I've understood that part... what I am wondering is if I have 3 hosts in one data center and 3 hosts in another, and I have asked for redundancy of 3 copies, is there a way to ensure all three copies are never in the same data center all at the same time.

Tracked it down to it thinking there was a pool version mismatch... then when I tried to transition to a new master it would fail with Xmlrpc_client.Connection_reset ... digging deeper it was complaining that it couldn't restore from the wrong version.

Lots of head banging later... I setup a backup for the pool metadata and forced the backup immediately. TADA... I can now change the master with no issues at all.