Mix PX 2.3 and 3.0 before upgrade cluster

Hi at all !!!

Situation: 2 node PX 2.3 (very last 2.3 subversion), run several VM on node 1 and 2.
I need to insert node 3 (blade system).
Is impossible to migrate all node 2 (or 1) VM to a single node, I will proceed to an hot upgrade without turn off VM.


Case 1:
Insert node 3 on Proxmox 3, can I migrate node 2 (or 1) VM to node 3 ? Live migration from 2.3 -> 3.0 ?
Then I upgrade node 2 and than node 1.

Case 2:
Insert node 3 on Proxmox 2.3, the same version on nodes 1-2-3, migrate VM and upgrade nodes 1-2-3.

what is the best solution?

Very thanks

Luca