Simple definition
Cluster Shared Volumes (CSV) allow multiple Windows Failover Cluster nodes to access shared storage, commonly to host Hyper-V virtual-machine files.
Technical operation
The cluster coordinates access to a shared volume, typically visible under C:\\ClusterStorage. Shared access does not mean unrelated VMs should write concurrently to the same VHDX.
The cluster controls membership, resources, and access paths. Under some conditions, I/O is redirected through a coordinating node. Network, storage, quorum, and multipathing architecture must be planned together.
Practical example
For example, two Hyper-V hosts access VM disks on a CSV. If one host fails, another may restart the workload when the cluster, shared storage, and necessary capacity remain healthy.
Best practices and limitations
CSV is not a backup and does not protect against shared data corruption. Use application-consistent backups, storage-path monitoring, and rehearsed failover tests.