USB hard drives, so popular yet little known. I would get around by explaining what USB is in the first place so we can move on to the more complicated matter. USB is a connector type to exchange data. It is designed to be universal as it says in the name, Universal Serial Bus. First time it was standardized many companies joined in to make sure it can be used on every device they manufacture. First version of it allowed 1.5 megabits per second which was astonishing at that time, leaving 115 kbit per second serial port in dust.

Second version called 1.1 sported a fancy 12 megabits a second transfer rate but it didn’t take really long until the 2.0 emerged. With its 480 Mbits per second, or 60 megabytes it proven its worth during the years and now is considered an industry standard. Any device that needs to communicate with a computer or any other standard device either uses some kind of this connector or firewire. Firewire has been outperformed by USB 2.0 by a lot, and according to Wikipedia somewhere around 2.5 billion usb capable devices are sold every year.

An usb hard drive realizes connection with the computer through this kind of connectivity. By definition an usb drive is an external device therefore lies in its own casing. Which holds the USB to PATA or SATA translation between the casing and the hard disk drive residing inside. Smaller USB hard disks are powered through usb, but this is not usual since maximum current permitted on any usb connection is 1 A and with 5v voltage it means a total of 5 watts passed to devices. Laptop hard drives are able to work on this kind of power, but lots of external drives follow the 3.5” desktop form factor, and are drawing anywhere between 5 and 10 watts of power.

These devices are powered through an eternal AC-DC adapter, which transforms alternating current to direct current required by the hard disk. It acts as a sort of power supply unit. An USB hard drive is recognized upon connection by most current operating systems no additional software needs to be installed, thus making the use of these devices fool proof.

Most external hard drives at the writing of this article range in capacity from 160 gbyte to 1.5 terabyte. Just for comparison, a 1.5 terabyte drive can store the content of approximately 330 DVDs.