Western Digital’s Mybook Thunderbolt Duo external storage design that can carry two HDDs under a single external case. Today, the world’s leader for external storage solution is bringing the device officially out for us, for the price of $600 for the 4TB (2x2TB) variant while $700 for 6TB (2x3TB). Aside from its two-in-1 storage support, Mybook Duo’s other feature includes “daisy-chaining” up to six of its units on your Mac. In our previous report, we got news that the device allows 30-second transfer of full HD movies including support for other optical connections such as HDMI, VGA, and DVI. Meanwhile, its PR suggest the product supports RAID 0,1 including JBOD options for folks who run Windows on OS X plus, daisy-chain with your Mac’s Time Machine backup storage which is quite handy especially for users who needs a large storage solution in their computers.