Those Thunderbolt accessories that have been desperately missing are finally starting to see the light of day. Western Digital today announced a new product in the MyBook line, the Thunderbolt Duo. Why Duo? The unit features two hard drives that you can utilize in different ways. Either you can the RAID 0 mode and get the maximum capacity and speed out of both disks, or use RAID 1 to mirror the contents of one disk to the other for backup purposes.