Volume Shadow Copy
Volume Shadow Copy Service (VSS) manages and implements Volume Shadow Copies used for backup and other purposes.
- A computer can be backed up while applications and services are running (Only if the selected files are on a NTFS filesystem)
- Files open at the time of the shadow copy appear closed on the shadow copy volume. (Because the Shadow Copy Volume is an image created from the files selected for backup)
- Files are not skipped during the backup process (Except when not enough available space for creating the Shadow Copy Volume)
- The need for scheduling a backup window is eliminated. A backup window requires that applications be shut down to ensure a successful volume backup.
Note to see the current volume shadow copy backups along with installed shadow copy writers/providers use this command:
Note if the service is disabled then NTBackup will not be able to function and an error will be posted in the Event Log. It is possible to configure Ntbackup to not use Volume Shadow Copy:
[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Control \BackupRestore]
UseMicrosoftProvider = 0
More Info MS KB833829
Note if performing a defrag of a volume containing shadow copies, then the defragger can trigger the Volume Shadow Copy service to record all the cluster moving, which will fill the entire shadow copy storage area. VSS will delete the oldest shadow copies to make room, so all or some shadow copies will be lost. Changing the cluster size to 16K for the volumes containing shadow copies should solve the problem. More Info MS KB312067
Note if the Volume Shadow Copy service (VSS) is activated while a defrag is performed, then the defragger might stop before it is completed. VSS is activated when a backup operation is being performed, so either wait for this operation to complete or disable the VSS momentarily while running defrag. Defrag will show this following message while waiting for VSS to finish:
Paused for Volume Shadow Copy
More Info MS KB838421
More Info MS KB887013
More Info MS Technet - What Is Volume Shadow Copy Service?
More Info MS Technet - How Volume Shadow Copy Service Works
- vssvc.exe (VSS)