What Is the Purpose of an External Hard Drive?

By Shawn M. Tomlinson

An external hard drive can make your home computer a much better, user-friendly component of your life. External hard drives allow you to quickly back up all of your data. Your home computer can load faster and not be bogged down by projects that take up a lot of memory. By using multiple external hard drives, you can store a wide range of projects, including photos, videos, movies or even a TV series.


Since the dawn of the personal computer, users have wanted and needed more storage space for data than they have had inside the computer. It's inevitable. The more work you do on a computer, the more data and files you accumulate. Storing this data on removable media (first on floppy discs, then on compact discs or digital video discs and now Blu-Ray disks) means cataloging, with not always instant access to it. External hard drives solved that dilemma.


External hard drives can be thought of like file cabinets. You put all of your data in files that are out of the way and organized; yet, you can access it at any time. Because external hard drives typically have more storage capacity than removable media, it is easy to store a lot of data.


The inside of an external hard drive essentially looks like an old-fashioned multiple record player. They have several media discs inside, with an arm like a stylus that accesses the data stored on each one. Early external hard drives had a few megabytes (mb) of storage capacity. Over the years, as data files have become more complex and larger, external hard drives have grown substantially. They have gone from a few megabytes to gigabytes (gb) and now to terabytes (tb). The original 3.5-inch floppy disk could handle 400 kilobytes of information. That doubled to 800k a few years later, and then to 1.4 megabytes. Other removable media came into play with bigger capacities, so hard drives kept growing. A 10 mb hard drive held as much as 25 times the data of a 400k floppy. A 10 gb drive holds as much as 25,000 times that same floppy and a 1 tb drive can hold 250,000 times.


External hard drives are connected via a universal serial bus (USB), Firewire or wireless network to your computer. Early USB connectors transferred data at a rate of 1.5 megabytes per second (mps) or 12 mps. In 2001, USB 2.0 increased that rate to 480 mps. Firewire, which has the advantage of being able to "piggyback" multiple peripherals, originally transferred data at 400 mps and now is up to 800 mps. Wireless connections are dependent on the router and processor speeds. The speed at which data is transferred by any means also depends on the rotational movement of the drives. Average external hard drives move at 5,400 revolutions per minute (rpms); newer external hard drives have speeds between 7,200 rpms and 9,600 rpms.


External hard drives are best for storing data other than in the computer's hard drive or on removable media. Because of their speed and ability to be connected to any computer, external hard drives make highly efficient back-up units for internal or other external drives.

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