Planning to Back Up Open Files
Updated: March 28, 2003
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Open files are files that are normally skipped during the backup process. This is usually because the files are locked by a service or application, such as an operating system, word processing program, or application database. In Windows 2000 and Windows NT 4.0, if the operating system could not back up a file that was locked by an application, the file was skipped, and thus not backed up. In Windows Server 2003, open files are backed up by using the Volume Shadow Copy service.
When a backup is initiated by an application that can use the Volume Shadow Copy service, such as the Backup program in Windows Server 2003, the Volume Shadow Copy service makes a shadow copy of the volume to be backed up. The shadow copy constitutes a read-only copy of the volume data that is read by the backup application during the backup job. Applications can continue to access the files on the volume itself, uninterrupted by the backup. After the backup is completed, the shadow copy of the volume is deleted, because it is no longer needed. The backed-up data is stored on the backup media.
By default, Windows Server 2003 temporarily consumes free disk space on a volume for the shadow copy. The amount of disk space consumed depends on the amount of data that changes on the volume during the backup.
In the event that a shadow copy is unsuccessful, for example, when there is not enough temporary disk space available on the volume, Backup continues without using shadow copy techniques and, as in previous versions of Windows, reads files from the original volume and does not back up any open files.
To take advantage of open-file backups, purchase a backup application that works with the Volume Shadow Copy service.