5.1. Clustering overview

As a cluster-aware application, a SQL Server instance can be installed into an existing Windows cluster, creating what's referred to as a failover clustering instance. Once installed, the instance is accessed using a network name (aka virtual server name) without needing to know which of the underlying physical cluster servers the instance is currently running on.

The abstraction between a physical and a virtual server is a key component in providing continued database availability after a failure event. In the event of a server failure, the SQL Server instance automatically moves, or fails over, to another cluster server, while continuing to be accessed using the same virtual server name.