- External USB hard drives are enclosures that provide protection and connection for a Serial ATA hard drive (Serial Advanced Transfer Attachment). The inner hard drive of the USB enclosure resembles a typical computer hard drive, with magnetic recording material that stores data onto the surface of the disk. USB hard drives require a significant amount of power to run the Serial ATA drive and transfer data via USB, so most external hard drives will come with a power supply that plugs into a standard wall outlet.
- Serial ATA hard drives usually connect to a computer through the internal motherboard, but since computers do not have Serial ATA ports on the outside, external drives must use another type of connection. Inside of a USB hard drive, the Serial ATA connection on the hard drive is converted to a standard USB 1.0 or 2.0 port. So when a user plugs a USB cable into the external hard drive's port, the user is actually plugging directly into the internal Serial ATA hard drive.
- In order to transfer data between an external USB hard drive and a computer, a user must connect the two devices using a standard USB cable. After the USB cable is plugged into a free port on the computer, the hard drive can be turned on. The external hard drive will receive power from the wall outlet connection and begin transferring data through the cable. The computer will recognize that a storage device has been connected and will open a new window where the user can manage the hard drive's file. When a file is transferred between the computer and the hard drive, bytes of data travel through the USB cable and are stored on the magnetic material of the Serial ATA drive.