What an HA pair is

An HA pair is two storage systems (nodes) whose controllers are connected to each other either directly or, in the case of a fabric-attached MetroCluster, through switches and FC-VI interconnect adapters.

You can configure the HA pair so that each node in the pair shares access to a common set of storage, subnets, and tape drives, or each node can own its own distinct set of storage.

Depending on the model, nodes are connected to each other through an NVRAM adapter, gigabit Ethernet connections, or, in the case of systems with two controllers in a single chassis, through an internal interconnect. This allows one node to serve data that resides on the disks of its failed partner node. Each node continually monitors its partner, mirroring the data for each other’s nonvolatile memory (NVRAM or NVMEM).