VSS is a framework that enables application consistent snapshots of applications that provide a VSS writer. The CSV writer is the component that knows how to get data into an application consistent state before the FlashArray takes a snapshot. There is a writer for Active Directory, SQL Server, Hyper-V, and Cluster Shared Volumes. The Requestor, or backup application is what coordinates the backup activity. Many third party applications such as Veeam and Commvault can leverage Pure’s hardware VSS Provider. The builtin diskshadow utility can be automated to take an application consistent snapshot of the Hyper-V cluster’s CSVs, placing the VMs in a good state before the hardware snapshot.