CSV (Cluster Shared Volumes) is a feature in Windows Server in which shared disks are concurrently accessible to all nodes within a failover cluster. The feature was first introduced in Windows Server 2008 R2 as a way to simplify storage with clustered Hyper-V virtual machines (VMs).
In a cluster without CSV, only one node can access a disk LUN at a time, so multiple disks are required for migration. With Cluster Shared Volumes, storage is simplified because multiple nodes can access the same disk at once and fewer overall disks are needed. CSV can also reduce potential disconnection time when performing a live migration of VMs. Cluster Shared Volumes offers resiliency benefits by creating multiple connections between nodes and the shared disk, meaning that if one part of a network goes down, communication can be accomplished through another part of the network.
CSV requires NTFS, but there are no hardware requirements beyond what is needed for a failover cluster.