Hello,
Accoding to page # 73 of the user’s manual only WD Red and/or WD Green are supported.
“Important: Only use WD Red™ or WD Green™ hard drives to replace the drives in your My Book Duo device enclosure. Also, replacement drives must be new, and the same capacity as the drive that failed. The RAID configurations require both drives to be the same capacity. Using any other hard drive or capacity voids the Warranty for your My Book Duo device.”
