Size of the backed up data is larger than the source data

Problem

The size of the backed up data of a source drive is larger than the actual data on that drive.

Cause

Volume Shadow Copy Files on the volume are also being backed up. This can be verified by mounting the recovery point, shadow copy files can be found in the System Volume Information folder.

Solution

Add path of the Volume Shadow Copies folder in registry "FilesNotToSnapshot" :

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry.

1. In Windows, click Start and then click Run.

2. Type Regedit.

3. Click OK.

The Registry Editor opens.

4. Navigate to the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshot\ 

5. Add a new "REG_MULTI_SZ" value :

Value Name : "Volume Shadow Copy Data"

Value Data : "$AllVolumes$\System Volume Information\* /s"

More details about this registry can be found in Microsoft's article : Excluding Files from Shadow Copies