WD My Book Thunderbolt Duo full review

If there’s one thing faster than a hard disk attached to a Thunderbolt cable, it’s two disks attached to the new lightning-speed connector.

That’s how Western Digital has managed to garner SSD-like speeds from the WD My Book Thunderbolt Duo, a desktop storage solution sporting two internal 3.5in hard disks.

The unit follows the now-familiar Western Digital book-as-storage metaphor, a broad volume with rounded spine and a series of morse dashes tracing all around the page leaves. 

Build quality is not as upmarket as the mock-metal case may first suggest – in contrast to WD’s handsome My Book Studio, also pitched squarely at Mac users, the WD My Book Thunderbolt Duo drive is an all-plastic affair sprayed silver in an attempt to match real metal Macs. 

By depressing the top of the case, a lid pops open to let you replace a disk when required. We tested a model with two 2TB WD Caviar Green drives inside; it’s also available in 6TB total size, made from two 3TB disks.

These disks are not the fastest of SATA drives but run comparatively quiet and cool, and combined with the fanless design ensure that the drive won’t drive you to distraction through rumbling operation.

Unlike the G-Tech Thunderbolt drive, which is configured using OS X’s Disk Utility for software RAID, the WD My Book Thunderbolt has its own software for Windows and Mac to help setup and maintain the unit.

You can use the WD Drive Utilities software to switch between RAID 0 for 4TB of speed and capacity, RAID 1 for 2TB of data security, or JBOD to just use the two disks independently. 

Format options are HFS+ with Journaling, native for OS X; and ExFAT, an updated version of Microsoft’s FAT that can address the huge disks available as well as the >4GB files you’ll want to store on them.

WD’s software can also execute a secure wipe of the disks and give SMART diagnostic information on their health.

Using the drive just requires powering up from the included external 12V mains adaptor plug, and connecting to any Mac or Windows PC with a Thunderbolt port. The required Thunderbolt cable is not included.

WD My Book Thunderbolt Duo: Performance

We first tested the Thunderbolt Duo in JBOD mode to check the performance of a single disk. In the QuickBench test in OS X, read/write speeds were both around 110MBps across a range of file sizes from 256kB to 100MB. Peak speeds were found with the largest files in that range, reaching up to 112MBps.  

Another useful gauge to performance is with small file transfers, focusing on sequential and random, where the WD My Book Thunderbolt Duo showed an average of 90/92MBps sequential, and 17/64MBps random transfers for respective read/writes.

Fastest speeds were seen in RAID 0 mode, measuring up to 223MBps sequential reads and 217MBps for writes.

This setup also saw faster small-file performance, averaging 154/158MBps sequential and 46/63MBps random, for datasets from 4kB to 1024kB.

To confirm real-world performance, we copied a Blu-ray film from an SSD-equipped Mac mini to the WD My Book Thunderbolt Duo drive.

The 23.24GB directory of video and metadata transferred in 1 min 46 sec, suggesting an average rate of 220MBps. That’s a great result and almost twice the write speed of Elgato’s Thunderbolt SSD.


WD My Book Thunderbolt Duo: Specs

  • 4TB external desktop drive
  • 2x 2TB WD Caviar Green SATA disks
  • 2x Thunderbolt
  • RAID 0, 1 or JBOD
  • 12V DC mains adaptor
  • 165 x 157 x99mm
  • 2.15kg

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