Western Digital’s My Book Thunderbolt Duo is about as big as WD’s My Book Studio II, and the two drives have similar cases, The obvious difference are the different activity indicator lights on the front of each drive. The other major difference is that the My Book Thunderbolt Duo, as the name indicates, has Thunderbolt connectors—two of them, to be exact.
With its two Thunderbolt ports, the My Book Thunderbolt Duo easily fits into a Thunderbolt daisy chain. However, the drive has only Thunderbolt. It doesn’t have USB or FireWire, so the My Book Thunderbolt Duo can be used only with Thunderbolt Macs
WD uses a pair of Caviar Green drive mechanisms in the My Book Thunderbolt Duo. The drives are configured by default as a RAID 0, which gives you the maximum amount of storage as well as fast performance. You can reconfigure the drive as a RAID 1, where one drive duplicates the data on the other drive, and this provides data protection, but you essentially cut the available storage in half. You can also set up the My Book Thunderbolt Duo as a pair of separate drives that mount on the desktop (a configuration called JBOD). We tested a 6TB ($700) drive, but a 4TB ($600) version is also available.
According to WD, the Caviar Green drive mechanisms are designed to use less energy than other mechanisms in the company’s lineup, such as the Caviar Black. The Caviar Green drives also allow WD to avoid using a fan in the My Book Thunderbolt Duo, which helps cut down on noise from the drive. If a drive mechanism fails, you can replace it yourself easily, but you can use only Caviar Green drive mechanisms.
In our series of lab tests, the My Book Thunderbolt Duo had decent transfer speeds, especially in comparison to USB 2.0 and FireWire 800 drives, but when compared to other Thunderbolt drives, the My Book Thunderbolt Duo fell to the back of the pack. In the AJA System Test, the drive clocked a write speed of 235.6 MBps and a read speed of 244.3 MBps. When writing a 10GB file, the drive’s transfer speed was 201 MBps, and 184 MBps to read the same file. The write/read speeds for a 10GB folder were 184.4 MBps and 156.1 MBps, respectively.
When compared to other Thunderbolt drives we’ve tested, the My Book Thunderbolt Duo has its share of ups and downs. Up: It tied for the fastest result in our 10GB file read test, keeping pace with a SSD RAID array. Down: Its result in our 10GB file write test was one of the slowest. Up: It was among the top performers in our 10GB folder read test. Down: It finished in the lower tier in our 10GB folder write test. And unfortunately, the My Book Thunderbolt Duo beat only one other Thunderbolt drive in our AJA System Tests.
Benchmarks: Thunderbolt storage devices
Write 10GB file
Read 10GB file
Write 10GB folder
Read 10GB folder
WD My Book Thunderbolt Duo
G-Technology G-RAID with Thunderbolt
LaCie 2big Thunderbolt
LaCie Little Big Disk SSD
LaCie Little Big Disk HD
Promise Pegasus R6
Seagate GoFlex Desk FW800
All scores in MB per second. Larger number is better. Best results in red.
We connected each drive to a 2011 17-inch 2.4GHz Core i7 MacBook Pro running OS X 10.7.2 with 4GB of RAM and an internal 250GB SSD. We timed the copy of a 10.77GB Zip file to the external drive and then timed copying the file back to the internal. We did the same with a 10.77GB folder of 7,420 smaller files. We then used AJA System Test with the Video Frame Size set to 1920 by 1080 10-bit RGB and a file size of 2GB.—Macworld Lab testing by James Galbraith and Kean Bartelman
Macworld’s buying advice
The My Book Thunderbolt Duo isn’t the most consistent performer, but its flexibility (two Thunderbolt ports; RAID 0, 1, and JBOD support; user-replaceable drive mecahisms) make it an attractive option for users with Thunderbolt-enabled Macs.
Editor’s note: Updated 4/24/12 at 9:15 p.m. PT with revised buying advice.
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