External hard drives—or external hard disks, as they are sometimes called—offer computer users large amounts of portable data storage. They are identical to internal hard drives, except that they are housed in disk enclosures and are connected to your computer via a USB cable.
A portable hard drive is favored by computer users with unusually large data storage needs and by people who want a safe and reliable means of backing up the files stored on their computer's built-in hard disk. You have many options if you want a backup hard drive, from units with terabytes of storage capacity to small flash memory sticks with varying amounts of space.
Must-Have Features of External Hard Drives
If you're going to buy an external USB hard drive, know that the specifications used to define their features are identical to those used for internal hard drives. The only functional difference between the two is that regular hard disks are permanently mounted inside your computer case, while external drives can be connected and disconnected as needed via a USB cable, creating portable data storage.
Storage capacity is measured in gigabytes (GB) or terabytes (TB). The greater an external hard drive's storage capacity, the higher its price, so you should make an honest evaluation of your data storage needs to select the most cost-effective product.
You'll also need a working understanding of retrieval rates to evaluate the suitability of a given product. The two specifications used to express a hard drive's retrieval rates are gigabytes per second (GB/s) and revolutions per minute (RPM). The more GB/s a hard drive can retrieve, and the higher the RPMs at which the hard drive functions, the faster, more efficient (and more expensive) it will be. However, by nature, external hard drives are functionally slower than internal drives when connected to your system, even if they have identical specifications.
External Hard Drive Options
If you use a Mac, you can get a FireWire hard drive. FireWire is a branded technology of Apple, Inc., but Sony and Texas Instruments produce drives using identical technology. Sony's is known as the i.Link hard drive and Texas Instruments' is called the Lynx hard drive.
Also, while ATA and SATA hard drives are the most common, you can take advantage of an alternative technology known as the SCSI hard drive. SCSI is an acronym for "small computer system interface," and it is excellent for high-performance computers and servers, as it offers advantageous speed, bus width and device connection capabilities.
Top Manufacturers of External Hard Drives
Apple, Sony, Texas Instruments, Hitachi, Seagate, Western Digital, Dell, Gateway and Hewlett-Packard are all well-known manufacturers of hard drives.