Windows Vista I/O Technologies - Shadow Copy

Shadow Copy

A number of Microsoft Windows components have been updated to make use of Shadow Copy. The Backup and Restore Center in Windows Vista and later performs block-based backups when doing full system backups. The file backup feature also uses shadow copy but stores files inside ZIP files.

Beginning with Windows Vista, Shadow Copy is also used by the System Protection component which creates and maintains periodic copies of system and user data on the same local volume (similar to the Shadow Copies for Shared Folders feature in Windows Server) but allows it to be locally accessed by System Restore. System Restore allows reverting to an entire previous set of shadow copies called a Restore point. Prior to Windows Vista, System Restore was based on a file-based filter that watched changes for a certain set of file extensions, and then copied files before they were overwritten.

Additionally, a property sheet shell extension called Previous Versions allows restoring individual files or folders locally from the restore point, as they existed at the time of the snapshot, thus retrieving an earlier version of a file or recovering a file deleted by mistake.

The shadow copy is not created every time a file is changed; backup copies are created automatically once per day, or manually when triggered by the backup utility or installer applications which create a restore point. The "Previous Versions" feature is available in the Business, Enterprise, and Ultimate editions of Windows Vista.