Shadow Copy

Volume Shadow Copy Service (VSS ), called in localized versions of Windows Volume Shadow Copy and colloquially simply as " Shadow Copy ", is a term introduced with Windows XP system services to generate and deployment of Version objects.

More details

The Volume Shadow Copy service was introduced with the Windows XP operating system and then provided in an extended version with Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2012. It is used for the easy creation and deployment of version objects (called snapshots). As part of the hard disk capacity previously provided this service saves modifications to files and folders as part of up to 64 shadow copies, so older version stands.

The shadow copies themselves are read-only. The advantage of this technique lies primarily in the fact that users can recover overwritten older versions of a file independently without having to rely on an intervention by an administrator.

In addition, the Volume Shadow Copy service can be used to create backups of consistent states of file systems or metadata that can otherwise be blocked by write operations (such as the registry or the system databases ).

For this, programs can implement so-called " VSS Writer" to store copies of the currently opened files in a consistent state in the shadow copy. The SQL Server provides, for example, such a component. Some copy programs use this functionality to clone systems in operation.

In Windows XP a highly restricted version of VSS is included. Permanent storage by older version status is not possible. From each logical drive only a temporary shadow copy can be created. This will, for example, backup solutions like Acronis, SEP sesam, NTBackup, long Meier backup, ShadowProtect, Bacula, Duplicati and SyncBack Pro used to back up all files during operation can consistently. A shadow copy can be created for versions prior to Windows Server 2008 via the command line program vshadow.exe from the VSS SDK. In more recent versions is " Vssadmin.exe " already exists on the system, " vshadow.exe " works at least not in the 64- bit operating system version.

It should be noted that Microsoft's VSS abbreviation used for Visual SourceSafe.