Why You Can Trust CNET WD My Book Thunderbolt Duo review: WD My Book Thunderbolt Duo
WD My Book Thunderbolt Duo
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.
The Good
The Bad
The Bottom Line
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 |
| Connector options | Thunderbolt |
| Size (WHD) | 3.9 x 6.5 x 6.2 inches |
| Weight | 5.2 lbs. |
| 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.
Performance
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.
When set up in RAID 0, the My Book Thunderbolt showed its top performance scoring some 168MBps when moving data over from the Pegasus R6, which is the fastest Thunderbolt storage device on the market to date. When I took the R6 out of the daisy chain and tested the My Book by itself, by copying data from one place to another within the drive, forcing it to do both reading and writing at the same time, it registered around 77MBps. Both of these numbers are faster than many other internal drives, but were slower than those of the LaCie 2big Thunderbolt.
Still in RAID 0, the My Book Thunderbolt scored 156MBps and 167MBps for writing and reading, respectively, when it tested against the MacBook's internal drive. These numbers were noticeably lower than those of the LaCie counterpart.
As expected, the My Book Thunderbolt performed worse in RAID 1. When coupled with the R6, it scored some 101MBps; when working by itself doing both writing and reading, it was just a measly 40MBps. These were the slowest on the charts, even slower than internal hard drives.
Still in RAID 1, when tested again the MacBook's internal drive, the My Book registered 108MBps for writing and 109MBps for reading, about the slowest among Thunderbolt devices but still significantly faster than non-Thunderbolt external storage devices, including those using USB 3.0 and eSATA.
Overall, however, the WD My Book Thunderbolt is still very fast and in most cases faster than you need. The drive also worked well in my testing and generated very little heat..
(Longer bars indicate better performance)
 | Unit to unit | | Self read and write |
(Longer bars indicate better performance)
| Read | | Write |
Service and support
The length of the warranty is the most important thing for storage devices, and Western Digital sort of delivers this time around. The company backs the My Book Thunderbolt Duo with a three-year warranty, which shorter than what it offers the My Book Studio Edition II. At the company's Web site, you'll find a section dedicated to the drive where you can find all you need in terms of support.
Conclusion
While among the slowest of the half a dozen Thunderbolt storage devices on the market, the WD My Book Thunderbolt Duo still makes a very good choice for Thunderbolt-enabled Mac owners. The drive is faster than any non-Thunderbolt external storage devices on the market, has a flexible design, and costs significantly less than its peers.