Western Digital has rolled out one its My Book external hard drives, this time packing a pair of disks in RAID configuration to guard against data loss.

The My Book Mirror Edition contains two terabyte drives, though since they form a RAID 1 array, you'll only get 1TB of storage capacity. Copy your content to the drive, and what's written to the first disk is also written to the second to ensure that if one of the two fails, you can still get your information off the other.

WD My Book Mirror Edition: back up your back-up

That said, if raw capacity's your thing, the drive can also be set to RAID 0, with blocks of data written across both disk's combined 2TB space - actually less than that, thanks to the formatting.

WD said the unit has a USB 2.0 interface and comes with Windows-friendly automatic back-up software. It's green too: WD claimed the unit's drives consume a third of the power that regular HDDs do.

Available now, the My Book Mirror Edition costs $290/£170. A 2TB (4TB in RAID 0) version costs $550/£310.

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