WSFC

Windows Server Failover Clustering (WSFC) is a Windows Server feature that provides high availability and scalability for clustered applications and services. A WSFC cluster consists of two or more servers, networked together and connected to shared storage or data-replication mechanisms. The cluster runs a common set of services that expose the clustered resources under a virtual network name and IP address. If a node fails, another node can automatically take over.

Key concepts include resources, resource groups (roles), and the cluster database. Resources represent services or applications; resource groups organize related resources. The cluster monitors the health of resources and, upon failure, fails over to another healthy node. Shared storage or coordinated replication ensures data consistency across nodes. Clusters can span sites in stretch configurations to support multisite disaster recovery, though latency and WAN considerations apply.

Quorum is a mechanism that determines whether the cluster can run. Typical configurations include Node Majority, Node and Disk (or Disk Witness) Majority, and Node and File Share Majority. Modern versions support dynamic quorum and dynamic witness to adapt to node changes without administrator intervention. Management can be performed with Failover Cluster Manager, Windows PowerShell cmdlets (for example, Get-ClusterResource, Add-ClusterNode, Set-ClusterQuorum), and Windows Admin Center.

Common workloads hosted on WSFC include SQL Server Failover Cluster Instances and Hyper-V failover clusters. WSFC enables rolling upgrades and coordinated management of clustered services, delivering higher availability and simpler recovery in the event of node or service failures.