A USB hard drive is a data storage device that uses connects to the computer through the USB port. Although it has the same capacity range as internal drives, it is more commonly used as a secondary or backup drive instead of primary storage. It is usually designed for mobile use, because it has high compatibility and is easily transferred between computers. Most models draw power from the computer through the USB interface instead of an external AC supply.
A desktop USB hard drive weighs approximately two pounds. It gets heavier as its storage capacity increases. It usually comes with a USB cable and may include a stand or dock. It has a storage capacity between 40GB and 400GB.
Portable USB hard drive
A portable USB hard drive is only slightly larger than a flash or thumb drive, usually small enough to fit inside a shirt pocket. It has a storage capacity between 6GB to 160GB. It has a built-in USB plug that connects directly to the computer instead of using a cable. It is commonly used for laptops, tablet and pocket PCs, and other portable devices.
