CLUSTERS
The following figure shows a two-server Domino cluster (Server 1 and Server 2) and a two-server active-passive operating system cluster (Server 1 and Server 1 Backup). In the operating system cluster, Server 1 Backup stands by to take over if Server 1 fails. Because Domino fault recovery is running on the Domino servers, the operating system cluster is configured to fail over only in case of hardware failure. (If Domino fails, fault recovery restarts it.)
The IBM® Lotus® Notes® client is using two databases on Server 1. Database A has a replica on Server 2 in the Domino cluster. Database B does not have a replica in the Domino cluster. If there is a hardware failure on Server 1, Domino clustering causes the client to fail over to Server 2 for access to Database A. Then operating system clustering causes Server 1 Backup to start, letting the client resume working in Database B. In addition, there are again two active servers in the Domino cluster so that Domino failover and workload balancing are available again.