When the Physical Disk of host is referenced by others (for example, if the file is open or there are processes referring a file in the current physical disk or partition), it tries to dismount the volume first. However, there are files referenced in current physical disk or partition, and the open-disk status makes the operation fail.
For issues faced with VMware Workstation 7.x, 8.x, and 9.x, disklib does not make a strict check for independent-persistent disk (Raw disk added). If files are referenced in current disk, open-disk fails.