In this configuration, one node, the primary node, supports all clients and one instance of Microsoft® SQL Server™, while its companion node, the secondary node, remains idle. This configuration provides the maximum availability performance for your resources. The secondary node is a dedicated backup ready to be used if a failover occurs. If the configuration of the secondary node is identical to that of the primary node, no performance degradation is seen by clients after reconnection.
For some mission-critical virtual SQL Server applications, using all available resources on the primary node and having all the available resources on the secondary node ready in the event of a failover is the most appropriate configuration. There are two additional configurations that can be considered:
Additional services that are not mission-critical may be running on the primary node. In the event of a primary node system failure, only those services configured to failover to the secondary node continue to operate. Clients using services installed on nonclustering shared drives lose access to those services until the node is brought back online. These services may include any application not considered to be mission-critical.
Applications that are not mission-critical may run on the secondary node. In the event of a failover, these critical services can be stopped as required to provide necessary resources for SQL Server.