Hard Drivin' (page 2)

Access time is the amount of time, measured in milliseconds, that it takes the drive to locate a specific piece of information on the disk. Access times have decreased gradually over the years, but appear to be leveling out. While each access is tiny, added together, they can affect the performance numbers of the drive. Access time is not as important for video, where a single millisecond access may be all that is required for a single huge transfer of data.

The number of platters a drive has corresponds to the density of the data at which the drive stores data. Drives with fewer platters are simpler to manufacture, but to store larger quantities of data on them, manufacturers must use some sophisticated storage methods, including advanced head designs and data encoding schemes. As a benefit to the end-user, drives with fewer platters are usually slightly quieter and generate somewhat less heat.

New drives include a buffer of solid-state memory, generally 2MB, but often as high as 8MB. The buffer accelerates read operations and provides a margin of security.

Not all external hard drives have power switches. Some are bus-powered, meaning that when you connect them to a FireWire or USB 2.0 interface, they will spin up and make themselves available to the computer without the need to plug them into the wall. Drives that use an AC adapter may stay on all of the time, even when your computer is off. A power switch would allow you to save some energy and may even save some wear and tear on the drive.

There you have it: a quick and dirty overview of some of the most important features to consider when shopping for an external hard drive. You can never have enough hard disk space, so when it's time to add some storage to your system, an external hard drive is, without question, one of the best and easiest upgrade you can make.

Charles Fulton is an Associate Editor for Videomaker Magazine.

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