RAID 0 (strip) offers top capacity and performance, but if one of the hard drives crashes, you'll lose data on both. The options are RAID 0 (default), RAID 1, and two separate volumes. The drive comes with WD Drive Utilities, which helps monitor the status of the drive and change the internal hard drive's configurations. Out of the box, the drive is configured in RAID 0 and preformatted using HFS+ it works immediately once plugged to a Thunderbolt-enabled Mac running OS X 10.6.8 or later. There's nothing to setting up the My Book Thunderbolt Duo. I haven't tried, but WD says that although other SATA hard drives physically fit in the slots, they are not tested to work with the chassis.

Users can replace these two hard drives with another one, as long as they use WD's Green drive. The trade-off is that they also tend to have slightly slower performance. They are called green because they're designed to use less energy than other drives of the same capacities. The internal hard drives used for the new My Book belong to WD's SATA Green drive family. The top of the drive can be opened with a push to reveal the internal drives inside. The My Book Thunderbolt doesn't have a power switch since it shares the power status of the computer it's connected to.

The only differences are the new tiny power/status light on the front (the previous model has a large vertical one) and the two Thunderbolt ports on the back (instead of USB, FireWire, and eSATA connection options). The WD My Book Thunderbolt Duo shares the same design as the My Book Studio Edition II it looks like a closed book that's standing up. 3.5-inch-based dual-bay external hard drive

Wd my book external hard drive 6tb