The issue occurs when you have a volume that is configured for deduplication in Windows and it is mounted on another volume. When you back up the other volume using the option Back up files and directories by following junction points and mount points, Backup Exec also backs up the mounted volume’s chunk store.
For example, you have a volume E:\ on a Windows Server 2012 computer which is configured for deduplication. A folder on the C:\ volume has mounted the E:\ volume. When you back up the C:\ volume, the chunk store on the E:\ volume gets backed up.
Deselect the mounted volume’s System volume information\Dedup folder in the job’s backup selections to ensure that Backup Exec does not back up the chunk store.
Note: When you back up the deduplicated volume directly instead of backing it up using a mount point, Backup Exec skips the chunk store automatically.