If you have two nodes on each site (SYSTEM1 and SYSTEM2 on the primary site, SYSTEM4 and SYSTEM5 on the secondary site), the Exchange database can fail over from SYSTEM1 to SYSTEM2 or vice versa on the primary site, and SYSTEM4 to SYSTEM5 or vice versa on the secondary site.

Figure: Cluster configuration on the primary site provides a view of an active-passive cluster configuration on the primary site.

Figure: Disaster Recovery environment displays an environment that is prepared for a disaster with a DR solution. In this case, the primary site is replicating its application data to the secondary site.

In a disaster recovery environment, the cluster on the primary site provides data and services during normal operation; the cluster on the secondary site provides data and services if the primary cluster fails. When a failure occurs at the primary site, the DR solution is activated. The data that was replicated to the secondary site is used to restore the application services to clients.

Figure: Application services restored after primary site failure illustrates this type of failure.

You can choose to configure replication using VVR or an agent-supported array-based hardware replication. You can use the DR wizard to configure VVR replication or required options for the VCS agents for EMC SRDF or Hitachi TrueCopy. To use the wizard with any other agent-supported array-based replication, you must complete configuring global clustering with the wizard before configuring replication on the array.