External Hard Drives combine all the conveniences of a real hard drive with the portability of a mobile storage device. Since they are real hard drives, they are available in the same sizes as internal hard drives. Although some External Hard Drives connect to a computer through a USB port, they also have the option to connect to the much faster eSATA and IEEE 1394 interfaces.
Much like their internal cousins, External Hard Drives are less likely to lose data to static electricity because hard drives are specifically designed for long-term storage. In addition, External Hard Drives can often be removed from their casing and installed into a computer in an emergency such as if an internal drive has failed.
Because of their power needs, External Hard Drives require external power reducing the convenience of using them as a portable storage solution. They are also much larger than flash drives often topping off at four pounds with dimension around 8 inches long by 5 inches wide by 1.5 inches wide. This is hardly a device that can be carried around in one’s pocket or around a neck lanyard. In addition, due to their weight, size, and the fact that they have sensitive moving parts, they are highly subjected to damage if dropped or bumped. Given that the whole package (hard drive and external case) can cost well over $100, users must be more careful than with much cheaper flash drives.