Not relevant (usually 1-node appliances)
Manual configuration (optional)
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.
DataCore, SSY [SDS]/10.0 PSP11, x86
Block Failure Protection, Reads/Writes, Data Availability