Do you ask about storage failover in HA pair or about "HA mode"? The former is of course enabled between partners in each HA pair. The latter can and need to be enabled on 2 node cluster (single HA pair) only.
Each aggregate has its owner node. When non-owner node receives service protocol requests, data will travel from owner node to requesting node through cluster interconnect networks(not HA interconnect). takeover and giveback occur inside each HA pair.