Western Digital My Book Thunderbolt Duo 4TB review

Thunderbolt and RAID combine for speed and capacity

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  • Beats FireWire 800 speeds
  • Can daisy-chain other devices
  • Improved access to replace a disk


  • Variable write speeds

The My Book Thunderbolt Duo is Western Digital's first desktop drive to use an ultra-fast Thunderbolt interface. In fact, it has two such ports, so the drive and an external display can be connected to a Mac with just one by daisy-chaining the display from the drive.

There are two disks inside, and WD has improved the marking and releasing of the mechanism that lets you in, should a disk need replacing.

They're configured as a striped array by default, for the full capacity of 4TB in a single volume, with the risk that everything is lost if one disk expires. However, it has tremendous speed benefits. With files of 2MB and larger, it averaged 298.4MB/second when reading, and 266.1MB/second when writing, but with large variation in write speeds, between 353.1MB/second down to a low of 217.2MB/second.

Fortunately, the supplied software enables you to easily reconfigure the hard disks as a mirrored array, halving the usable capacity and slowing transfer rates, but with the insurance of having two copies of your data. In this mode, read speeds averaged 189.1MB/second, and 126.4MB when writing. We found less variation in write speed in this mode. It peaked at 176.8MB/second, and hit a low of 111.7MB/second with a 100MB file.

The Thunderbolt Duo delivers speeds in excess of the equivalent FireWire 800-equipped Studio II drive, and it can be bought for £400, which isn't a huge premium.

However, its performance is inconsistent compared to some other Thunderbolt RAID arrays, such as LaCie's Little Big Disk Thunderbolt Series 240GB SSD, which are a better option when sustained high speed is essential.

Tech Specs

Product TypeDAS Array
Number of Total Expansion Bays2
Total Hard Drive Capacity Installed6 TB
Number of Hard Drives Supported2
Number of Hard Drives Installed2
Brand NameWD
Form FactorExternal
RAID Levels1, JBOD
Host InterfaceThunderbolt
Height99.1 mm
Width157.5 mm
Depth165.1 mm
ManufacturerWestern Digital Corporation
Product ModelWDBUPB0060JSL-NESN
Product NameMy Book Thunderbolt Duo Dual-drive Storage System
Product LineMy Book Thunderbolt Duo
Manufacturer Part NumberWDBUPB0060JSL-NESN
Manufacturer Website Addresshttp://www.wdc.com
Marketing Information

My Book Thunderbolt Duo delivers the optimum fusion of performance and capacity. This drive offers two Thunderbolt ports delivering the revolutionary data transfer speeds available only with Thunderbolt technology. Daisy chain multiple devices through My Book Thunderbolt Duo and enjoy nearly unlimited flexibility and performance in your creative life.

Weight (Approximate)2.26 kg