Two-Node Cluster With One Logical Host

The simplest SAP cluster configuration is a two-node cluster with one logical host, as illustrated in Figure 1-1. In this asymmetric configuration, the SAP central instance and database instance (collectively called the central system), are both placed on one node. NFS is also be placed on the same node. This configuration is relatively easy to configure and administer. A drawback is that the backup node is underutilized. In case of failover, the central instance, database instance, and NFS service are switched to the backup node.

Figure 1-1 Asymmetric SAP Configuration

Two-Node Cluster With One Logical Host and Development or Test SystemIn this configuration, the central system (the central instance and database instance) is placed on one node and a development or test system is placed on a backup node. The development or test system remains running until a failover of the logical host moves the central system to the backup node. This scenario is illustrated in Figure 1-2. In this configuration, you must customize the Sun Cluster HA for SAP hasap_stop_all_instances script such that the development or test system is shut down before the SAP central instance is switched over and brought up. See the hasap_stop_all_instances(1M) man page and "Configuration Options for Application Servers and Test/Development Systems" for more information.

Figure 1-2 Asymmetric SAP Configuration With Development or Test System