Enabling Volume Shadow Service (VSS) for Windows File System Backups

Use the Microsoft Volume Shadow Copy Service (VSS) to create consistent point-in-time copies of data known as shadow copies.

By default, the Windows File System Agent backs up data from the live volume and not from the snapshot of the volume.

Use VSS to back up local volumes in clustered and non-clustered environments.
VSS can be enabled only on New Technology File System (NTFS) and Resilient File System (ReFS) volumes. VSS cannot be enabled on File Allocation Table (FAT) or FAT 32 volumes.
If the Windows operating system fails to create a shadow copy of the data then a regular backup is run automatically. You will receive a corresponding message in the Event Viewer.
Locked database files are backed up in an inconsistent state when VSS is enabled.

If you have third-party snapshot providers available and you wish to use the Microsoft VolSnap provider, add the nUseVSSSoftwareProvider additional setting on the client computer.
Ensure that you have sufficient free space on the volume. During a VSS backup, the free space needed on a volume for the shadow copy is related to the duration of the backup and the amount of changes being made to the data objects (files, databases) that are being backed up. VSS snapshots capture and copy disk blocks that are being changed by other processes while the backup for a particular object is running. If the backup runs longer, there is increased disk activity (files or databases being changed). This causes VSS to copy more data blocks and therefore, use more disk space.

From the CommCell Console, expand Client Computers > client > File System > backup_set.
Right-click the appropriate subclient and click Properties.
In the Subclient Properties dialog box, select the Use VSS options check box and choose how you want to set up backups:

Options	Description
Use VSS for all files	Software snapshot creation may fail if the VSS service is unavailable or it is unable to quiesce a volume. In any of these situations, you can choose to fail the backup job, continue and reset the access time, or continue without resetting access time.
Fail the job	Backs up data by using the software snapshot. Backup job fails when the software is unable to create a snapshot.
Continue and reset access time	Archives files, based on access time, from the live volume instead of the snapshot. After backup, the access time of the files is reset to the original time before backup started.
Continue and do not reset access time	Default. Data is backed up from the live volume and the access time of a file does not reset until the backup completes. This action may have an undesired effect on applications that utilize file access time. For example, OnePass archives files based on access times. In this situation, use a software snapshot to perform a backup of all files.
For locked files	Uses VSS only to back up files that are still in use or locked by some applications or system programs. To back up individual DFS-R nodes, select the For locked files option as the files may be locked during the replication process. However, the DFS-R configuration is backed up during a system state backup. Last Access time of the files is not reset after the backup operation.