well there are some qwaks namely

this is exactly what he said, docker hard drives!
But I bought 2 and one has blown out in the first few seconds (just 20s and pfff goodbye). The other works without any problem.
Good to know: the disks are limited to 2.5 SATA2 speed (but accepts the SATA3) and a size of 1TB!
The working copy or backup gadget really is (it is not a ghost or copy paste, safety issue)
Strangely the power outlet is not standards (too small) ...
Personally, my biggest problem is that when you plug two disks, you can not disable one to put another (you know, right click on usb..etc device). In short, disable both at the same time to change.