Hello
If I understood well this is the expected behavior, Disk Agent will use VSS option as default for Windows 7\Windwos 2008 servers
Option: Use Shadow Copy
Select this option if you want to perform a point-in-time backup using Microsoft Volume Shadow Copy Service (VSS). VSS allows you to create shadow copy backups of volumes, exact point-in-time copies of files, including all open files. This means that the VSS mechanism finishes all pending I/O operations and holds incoming write requests during the preparation of a shadow copy volume. In this way, all files on the filesystem level are closed and unlocked during the shadow copy creation.
On Windows Vista, Windows 7, Windows 8, Windows Server 2008, and Windows Server 2012 systems, if an entire volume is selected for backup and this option is selected for the volume, Data Protector additionally ensures that data of each Windows server role or third-party application which stores its data on the volume is made consistent before being backed up, provided that a corresponding VSS writer is available. The same behavior applies when an entire client system is selected for filesystem backup.
This option is selected by default on Windows Vista, Windows 7, Windows 8, Windows Server 2008, and Windows Server 2012.