Active/active and high-availability terms

active/active configuration
In the Data ONTAP 7.2 and 7.3 release families, refers to a pair of storage systems (sometimes called nodes) configured to serve data for each other if one of the two systems stops functioning. Also sometimes referred to as active/active pairs.
cluster
In the Data ONTAP 7.1 release family, refers to a pair of storage systems (sometimes called nodes) configured to serve data for each other if one of the two systems stops functioning. In Data ONTAP 8.x, a cluster is a group of connected nodes (storage systems) that share a global namespace and that you can manage as a single virtual server or multiple virtual servers, providing performance, reliability, and scalability benefits.
HA (high availability)
In Data ONTAP 8.x, the recovery capability provided by a pair of nodes (storage systems), called an HA pair, that are configured to serve data for each other if one of the two nodes stops functioning.
HA pair
In Data ONTAP 8.x, a pair of nodes (storage systems) configured to serve data for each other if one of the two nodes stops functioning.