I am so glad to see that Western Digital has come out with an affordable thunderbolt solution!

Western Digital has a 4 Terabyte:

The 4 TB Thunderbolt Western Digital has 2 thunderbolt ports and even the option to run Raid 1 which acts as a backup of all of your files onto the second hard drive. Or even Raid 0 which is the best for speed!

And even a 6 Terabyte version!

The 6 Terabyte version also has the option to run Raid 1 and Raid 0! The 6 Terabyte also has 2 thunderbolt ports.

Western My Book Thunderbolt Duo 6 TB dual-drive storage

Western My Book Thunderbolt Duo 6 TB dual-drive storage Back

Does your Mac have thunderbolt?

Thunderbolt Port on Mac

You will need a Thunderbolt cable to run these hard drives with your thunderbolt enabled Mac.

What is Thunderbolt
and why do you need an external thunderbolt hard drive?

- Thunderbolt
is the fastest interface for transferring files from your Mac to your PC.

Looking for a cheaper alternative check these out: