WD My Book Thunderbolt Duo 4TB

It isn’t just SSDs that can make use of Thunderbolt’s high bandwidth. Hard disks set up as a striped RAID array can reach impressive read and write speeds, too, and that’s the arrangement you get in this drive.

WD has taken the essentials of its Studio 11 design and removed the selection of older interfaces with a couple of Thunderbolt ports. Along the way, it’s also taken time to make small refinements to the case.

WD my book Thunderbolt Duo 4TB

Inside you’ll find two 3.5 inch hard disks, held vertically in two bays with their small­est sides parallel to the base. That helps to minimize the drive’s footprint. The top opens to allow the disks to be replaced, and Western Digital seems to have appreciated the awkwardness of doing this on its Studio models: here, the point on which you press to unlock the hinged panel is clearly marked out with an inset square.

The Studio Il’s inches-long drive activity light has been replaced by a single small point of illumination. That’ll be a welcome change if the drive is going to sit in plain sight, as it’s less distracting.

Thanks to the second Thunderbolt port on the back, adding this drive to your setup leaves the possibility of daisy chaining other Thunderbolt peripherals, including one that has no second port of its own, or an external monitor that doesn’t provide the Thunderbolt Display’s handy pass-through.

The support software provided gives you a simpler way than OS X’s Disk Utility to reconfigure the drive as a mirrored array

The support software provided gives you a simpler way than OS X’s Disk Utility to reconfigure the drive as a mirrored array. You can check the SMART status of the disks, too, to keep an eye out for physical failure, and scan for bad sectors. However, unlike the Studio II, it doesn’t install an icon in the OS X menu bar to give immediate warning of any problems.

The use of relatively large 3.5inhard disks pays off when it comes to transfer rates. With the WD set up as a striped array (the fastest arrangement, but the least protective against data loss), we saw an average read speed of 305.8MB per second in our large file tests. The average write speed was 279MB per second. However, we saw a large amount of variation in the values that contributed to these figures. The speed of writing trailed off as test files grew larger. We saw this in the figures returned when the drive was reconfigured as a slower mirrored array, too.

It’s certainly capable of good performance, but the My Book’s transfer rates are too vari­able to make it a dependable choice when very high, sustained speeds are important exactly where Thunderbolt should help.

Details
Price	$541 inc VAT; 6TB $653
From	store.apple.com/uk
Info	wdc.com
Needs	Thunderbolt Mac * Mac OS X 10.6.8 or higher * Thunderbolt cable (not supplied)
Pro	User-replaceable disks with easy access * small footprint * pass-through
Con	Variable transfer rates
Rates	6/10