Bryan O'Connor | 21 April 2013
You use shadow copies to restore previous versions of files and folders. It is much faster to restore a previous version of a file from a shadow copy than from a traditional backup copy, which might be stored offsite. Files and folders can be recovered by administrators, or directly by end users.
One of the courses I teach is the
Microsoft Windows 2012 Installing and Configuring course, the
Microsoft designation is the 20410B
In the presentation, we look at restoring data from a Shadow Copy.
A shadow copy is a static image (or a snapshot) of a set of data, such as a file or folder. Shadow copies provide the capability to recover files and folders based on snapshots that are taken of storage drives. After a snapshot is taken, you can view and potentially restore previous versions of files and folders that existed at the time that the snapshot was taken.
A shadow copy does not make a complete copy of all files for each snapshot. Instead, after a snapshot is taken, Windows Server 2012 tracks changes to the drive. A specific amount of disk space is allocated for tracking the changed disk blocks. When you access a previous version of a file, some of the content might be in the current version of the file, and some might be in the snapshot.
By default, the changed disk blocks are stored on the same drive as the original file, but you can modify this behaviour. You can also define how much disk space is allocated for shadow copies. Multiple snapshots are retained until the allocated disk space is full, after which, older snapshots are removed to make room for new snapshots. The amount of disk space that is used by a snapshot is based on the size of disk changes between snapshots.
Because a snapshot is not a complete copy of files, you cannot use shadow copies as a replacement for traditional backups. If the disk containing a drive is lost or damaged, then the snapshots of that drive are also lost.
Shadow copies are suitable for recovering data files, but not for more complex data (such as databases), that need to be logically consistent before a backup is performed. A database that is restored from previous versions is likely to be corrupt and require database repairs.
The demonstration is available at the BryanQA Youtube site