In a typical example of a high availability cluster, you create a virtual SQL Server in an Active-Passive configuration. The active node of the cluster hosts the virtual server. The second node is a dedicated redundant server able to take over and host the virtual server in the event of a failure on the active node.

Figure: Active-Passive configuration illustrates a typical Active-Passive configuration.

SQL Server is installed on both SYSTEM1 and SYSTEM2 and configured as a virtual server (INST1-VS) with a virtual IP address. The SQL Server databases are configured on the shared storage on volumes contained in cluster disk groups. The virtual SQL Server is configured to come online on SYSTEM1 first. If SYSTEM1 fails, SYSTEM2 becomes the active node and the virtual SQL Server comes online on SYSTEM2.

The virtual SQL Server is online on SYSTEM1, serving client requests. The shared disks provide storage for the SQL Server databases. SYSTEM2 waits in a warm standby state as a backup node, prepared to begin handling client requests if SYSTEM1 becomes unavailable. From the user's perspective there will be a small delay as the backup node comes online, but the interruption in effective service is minimized.