1.4.5 N+1 Configuration (Star)

An N+1 or star configuration includes some number of active servers and one hot-standby server. The active servers and hot-standby server do not have to be configured identically. Figure 1-15 shows an N+1 configuration. The active servers provide on-going data services while the hot-standby server waits for one or more of the active servers to fail. The hot-standby server is the only server in the configuration that has physical disk connections to all disk expansion units.

In the event of a failure of one active server, the data services from the failed server fail over to the hot-standby server. The hot-standby server then continues to provide data services until the data services are switched over manually to the original active server.

The hot-standby server need not be idle while waiting for another Sun Cluster server to fail. However, the hot-standby server should always have enough excess CPU capacity to handle the load should one of the active servers fail.

Figure 1-15 N+1 Configuration