Microsoft Cluster Services (MSCS) on Windows Server 2003 provides failover clustering for SQL Server, ensuring database availability when hardware or software failures occur on the active node. Properly planned and tested, a SQL Server cluster can achieve 99.99% availability for mission-critical database workloads.
Cluster Planning and Quorum Configuration
A two-node active/passive cluster is the most common configuration for SQL Server. The passive node sits idle during normal operations, ready to assume the SQL Server workload within minutes of a failure. Shared storage, typically a SAN, hosts the database files and is accessible to both nodes through SCSI reservations or Fibre Channel zoning.
The quorum disk holds the cluster configuration and serves as the tiebreaker in split-brain scenarios. Place the quorum on a small, dedicated LUN on the shared storage. In Windows Server 2003, the majority node set quorum model offers an alternative for geographically dispersed clusters, but requires at least three nodes to maintain a majority vote.
Test failover thoroughly before placing the cluster into production. Simulate failures at every level: network adapter failure, storage path failure, SQL Server service crash, and complete node shutdown. Measure the actual failover time and verify that client applications reconnect to the new active node without data loss. Document the expected behavior for each failure scenario and train your operations team on manual failover procedures.