The WD My Book Thunderbolt Duo is basically the Thunderbolt version of the My Book Studio Edtion II. The drive offers up to 6TB of storage space (in RAID 0) and very good performance for an external hard drive. Compared with other Thunderbolt storage devices on the market, however, it's one of the slowest.
To make up for this, the drive starts at a low $600 for 4TB and $700 for 6TB; that's about $100 cheaper than the similarly configured LaCie 2big Thunderbolt . Like with Thunderbolt storage devices, you'll have to spend another $50 for a Thunderbolt cable.
This lower pricing and the fact that users can replace the internal hard drives by themselves make the WD My Book Thunderbolt Duo a very good choice for people who want to enjoy Thunderbolt-grade performance without having to spend too much.
Design and features
|Drive type||3.5-inch-based dual-bay external hard drive|
|Size (WHD)||3.9 x 6.5 x 6.2 inches|
|Available capacities||4TB, 6TB|
|Capacity of test unit||4TB|
|OSes supported||Mac OS 10.6.8 or later|
|Software included||WD Drive Utilities|
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. 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 My Book Thunderbolt doesn't have a power switch since it shares the power status of the computer it's connected to. The top of the drive can be opened with a push to reveal the internal drives inside.
The internal hard drives used for the new My Book belong to WD's SATA Green drive family. They are called green because they're designed to use less energy than other drives of the same capacities. The trade-off is that they also tend to have slightly slower performance. Users can replace these two hard drives with another one, as long as they use WD's Green drive. 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.
There's nothing to setting up the My Book Thunderbolt Duo. 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.
The drive comes with WD Drive Utilities, which helps monitor the status of the drive and change the internal hard drive's configurations. The options are RAID 0 (default), RAID 1, and two separate volumes. RAID 0 (strip) offers top capacity and performance, but if one of the hard drives crashes, you'll lose data on both. RAID 1 (mirror) is the opposite; you get just half of the total storage and slower performance, but your data safety is doubled.
I tested the My Book in two sets of tests. In the first set, it was stacked up against other Thunderbolt drives as well as internal drives, including solid-state drives (SSDs). In the second, it was tested the way any other none-Thunderbolt external storage devices are tested: against the test machine's internal drive. The drive was tested both in RAID 0 and RAID 1 configurations.
The reason for the first set of tests is the fact that Thunderbolt has a ceiling speed of 10Gbps, whereas the fastest internal drive caps at just 6Gbps of the SATA 3 standard. For this reason, it'd make more sense to test a Thunderbolt storage device against the other fastest possible storage solution, which currently is an internal drive, especially SSD, connected directly to a computer's motherboard. I used a 2011 MacBook Pro running OS X Lion, on a SATA 3 (6Gbps) SSD, as the test machine.