The Volume Shadow Copy Service (VSS) enables the backup of locked or open files allowing volume backups to be performed while applications on a system continue to write to the volumes.
Unitrends system protection software uses VSS to capture the server’s system state and open files during a file-level backup and to obtain a volume image during a bare metal backup.
No configuration steps are necessary to enable VSS to work with the system protection software. To confirm that the system agent is using VSS, from the agent menu on the Windows Server system, select Options > Snapshot Properties. You will see a message that reads: Snapshots are enabled using Microsoft’s VSS snapshot driver.