VSS filesystem backup and restore
Some applications are not aware of the Volume Shadow Copy service. Such applications cannot guarantee consistency of data during the creation of a shadow copy. The VSS mechanism cannot coordinate the activities of these applications in order to perform a consistent backup.
However, you can still benefit from the VSS functionality. The cooperation between the backup application and a shadow copy provider can be still used to assure a higher level of data consistency. Microsoft calls this state of data consistency “crash consistent data”. This means that the VSS mechanism commits all pending I/O operations and holds incoming writing requests during the preparation of a shadow copy volume. In this way, all files on the filesystem are closed and unlocked when the shadow copy is being created.
Microsoft Volume Shadow Copy functionality allows the creation of a volume shadow copy without the participation of the applications being backed up. In this case, the shadow copy volume is created and then backed up by Data Protector. This approach can be used with applications that are not aware of the VSS mechanism.
IMPORTANT:
When applications that are not aware of the VSS mechanism are being backed up, data consistency from the applications’ point of view cannot be guaranteed. Data consistency is the same as in the event of a power failure. Data Protector cannot guarantee any data consistency when applications are not actively participating in the creation of a shadow copy.
The consistency of data in a VSS filesystem backup is improved in comparison to a
The advantages of VSS filesystem backup are as follows:
•A computer can be backed up while applications and services are running. Therefore, applications can continue to write data to the volume during a backup.
•Files that are open are no longer skipped during the backup process because they appear closed on the shadow copy volume at the time of the creation of the shadow copy.
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