A Cluster Shared Volume is a shared disk containing an NTFS or ReFS (ReFS: Windows Server 2012 R2 or newer) volume that is made accessible for read and write operations by all nodes within a Windows Server Failover Cluster.
This enables a virtual machine (VM) complete mobility throughout the cluster as any node can access the VHD files on the shared volume.
This helps ensure seamless live migration since the physical disk resource does not need to be moved between nodes.
CSV increases the chance that a live migration will complete within the TCP reconnect window and ensure a seamless operation to clients.
CSV builds a common global namespace across the cluster using NTFS reparse point.