The WD My Passport Pro is more than just the first 4TB Thunderbolt bus-powered portable drive on the market, it's also one of the fastest Thunderbolt drives available.
Hosting two internal drives, the Passport Pro allows users to arrange them in different RAID setups or as separate volumes. In my testing with the default configuration of RAID 0, the My Passport Pro proved to be the fastest hard-drive-based Thunderbolt portable drive to date. On top of that, the rugged and convenient design -- even if it's a bit bulky -- means that you won't need a separate Thunderbolt cable.
If you don't mind the lack of USB support, the My Passport Pro is one of the best portable storage devices Mac users can get, especially at its current price ($430 for 4TB or $360 for 2TB). For more choices, check out this list.
Convenient and rugged design
As mentioned, the My Passport Pro comes in two capacities of 4TB and 2TB. Both versions are almost the same size (5.6 inches long by 3.5 inches wide), but at 1.7 inches deep, the 4TB drive is some 25 percent thicker than its little brother. It's also significantly heavier at 1.6 pounds, compared with the 2TB version, which was just 1 pound.
Bus-powered Thunderbolt portable drive
5.6 x 3.5 x 1.7 inches (4TB) or 1.1 inches (2TB)
1.6 lbs. (4TB) or 1 lbs. (2TB)
Capacity of test unit
Mac OS X 10.6.8 or later
The 4TB version has more girth because it houses two 15-mm internal drives (2TB each), whereas the 2TB version houses two 9.5-mm internal drives (1TB each). That said, the 4TB My Passport Pro is one of the bulkiest bus-powered portable drive on the market. Still, it's not huge and you can still carry it around quite easily.
The My Passport Pro comes in an all-aluminum chassis that's sturdy and good-looking. This casing also works as the drive's heat sink. On its underside, there's small area of openings for the air to come in, and on the front, there's a little ventilation fan that only runs when the drive gets hot.
There's no Thunderbolt port on the drive; instead, it comes with a built-in Thunderbolt cable that's always attached to the drive. This cable, when not in used, can be tucked away in the groove that runs around the sides. This is a great design that keeps the drive both aesthetically pleasing and convenient to use. Seriously, you don't need to carry any cables with this drive at all.
On the other hand, without an extra Thunderbolt port, you can't connect another Thunderbolt device to it. That means that in a daisy-chain setup (you generally can connect up to seven Thunderbolt devices together), the My Passport Pro can only be used at the end of the chain.