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How HA pairs relate to the cluster

HA pairs are components of the cluster, and both nodes in the HA pair are connected to other nodes in the cluster through the data and cluster networks. But only the nodes in the HA pair can takeover each other's storage.

Although the controllers in an HA pair are connected to other controllers in the cluster through the cluster network, the HA interconnect and disk-shelf connections are found only between the node and its partner and their disk shelves or array LUNs.

The HA interconnect and each node's connections to the partner's storage provide physical support for high-availability functionality. The high-availability storage failover capability does not extend to other nodes in the cluster.

Note: Network failover does not rely on the HA interconnect and allows data network interfaces to failover to different nodes in the cluster outside the HA pair. Network failover is different than storage failover since it enables network resiliency across all nodes in the cluster.

Non-HA (or stand-alone) nodes are not supported in a cluster containing two or more nodes. Although single node clusters are supported, joining two separate single node clusters to create one cluster is not supported, unless you wipe clean one of the single node clusters and join it to the other to create a two-node cluster that consists of an HA pair. For information on single node clusters, see the Clustered Data ONTAP System Administration Guide for Cluster Administrators.

The following diagram shows two HA pairs. The multipath HA storage connections between the nodes and their storage are shown for each HA pair. For simplicity, only the primary connections to the data and cluster networks are shown.

Possible storage failover scenarios in this cluster are as follows:

If Node1 and Node2 both fail, the storage owned by Node1 and Node2 becomes unavailable to the data network. Although Node3 and Node4 are clustered with Node1 and Node2, they do not have direct connections to Node1 and Node2's storage and cannot take over their storage.