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What is a System Image Backup?

A System Image Backup creates a backup image image of your disk volume, including the Windows system files (C:\Windows), your system settings, programs, along with any personal files or documents stored on the disk volume. You can restore your computer from the backup image.

Windows Server offers Windows Server Backup, which is basically the same thing with additional options and features.

How Windows System Image Backup Works

The Volume Shadow Service (VSS) creates a temporary snapshot of the original disk. The Windows Backup Engine (wbengine.exe) copies the temporary snapshot to a Virtual Hard Disk (VHD) file that is located on another hard disk, or on DVD, or on the network. The temporary snapshot ensures that the backup captures a single point in time.

If the VHD is located on a second hard disk, VSS creates a second persistent snapshot on the second hard disk. When making a subsequent backup from the same original disk to the same VHD, wbengine.exe coordinates with VSS to use the snapshot to store only the changed disk blocks from the original disk in the VHD. This allows you to make incremental backups that contain only the disk blocks that changed after the first backup. This can greatly speed up future backup operations.

To restore an older backup the old snapshot of the second disk used as the data source.

How Windows System Image restores the Windows volume (C:)

To restore a backup of the Windows volume (C:), wbengine.exe boots the computer into the Windows Recovery Environment (WinRE). WinRE opens the VHD file in the second disk that contains the backup data, copies the VHD file to C:, then reboots the computer.

How Windows System Image restores a data volume

To restore a backup of a data volume (not C:), wbengine.exe opens the VHD file contained in the second disk that contains the backup data, copies the VHD file to the original disk, then it dismounts the VHD file.

How Windows System Image restores an old Windows volume (C:)

To restore an old backup of the Windows volume (C:), wbengine.exe boots the computer into the Windows Recovery Environment (WinRE). WinRE exposes and mounts the old snapshot of the second disk, opens the VHD file in the old snapshot that contains the backup data, copies the VHD file to C:, then reboots the computer.

How Windows System Image restores an old data volume

To restore an old backup of a data volume (not C:), wbengine.exe exposes and mounts the old snapshot of the second disk, opens the VHD file contained in the snapshot of the second disk, copies the VHD file to the original disk, then it dismounts the VHD file and finally unexposes the enclosing physical snapshot.