Manual designation per Virtual Disk is required to accomplish this. The end-user is able to define which node is paired to which node for that particular Virtual Disk. However, block failure protection is in most cases irrelevant as 1-node appliances are used as building blocks.

SANsymphony works on an N+1 redundancy design allowing any node to acquire any other node as a redundancy peer per virtual device. Peers are replacable/interchangable on a per Virtual Disk level.