Microsofts Volume Shadow Copy Service (VSS) can be leveraged when using either array-based replication or vSphere Replication (VR). VSS operates at the block-level. The aim of VSS is to create consistent reliable snapshots by temporarily halting new writes and letting ongoing writes finish. Microsoft applications that support VSS are Active Directory, MSSQL, Exchange and SharePoint. VSS is also leveraged to create file system consistent snapshots of Microsoft NTFS volumes.