Examining Disk Storage Reliability Specs

By M. David Stone  |  Posted 2008-07-09 Print this article Print

Disk storage, whether on a corporate desktop or shared on a company network, is arguably the most important element of any computer system.

Computers are all about information: creating it, manipulating it, retrieving it and, above all, storing it. That makes storage, and more particularly hard disks, the most critical element of any computer system, a statement that holds true whether the drives are on the corporate desktop or function as shared storage on a company network, alone or in an array. If part of your job is deciding on minimum requirements for hard disks, that's a strong argument for paying close attention to hard disk specifications. Here's a look at some key reliability specs to consider.

Life Expectancy

Drives, like people, have a life expectancy. For drives, it's called the service life or design life (because that's how long the drive was designed to remain in service). The service life is typically three to five years, but can be as high as 10 years. Knowing the service life is important, because failure rates rise rapidly at the end of service life. Assuming the drive lasts that long, you'll want to replace it at that point-before it fails. Knowing the service life is also important for understanding the MTBF (mean time between failures) spec.

What Mean Time Between Failures Isn't

MTBF is probably the single most widely misunderstood drive spec, even among people who are knowledgeable about computer hardware. It doesn't tell you anything about how long a drive will last, which is what most people think it means. MTBFs for the current generation of hard disks are typically anywhere from 500,000 to 1.2 million hours for desktop drives, and as much as 1.6 million hours for enterprise drives. That works out to roughly 57 to 180 years. Drives obviously don't last that long.


M. David Stone is an award-winning freelance writer and computer industry consultant with special areas of expertise in imaging technologies (including printers, monitors, large-screen displays, projectors, scanners, and digital cameras), storage (both magnetic and optical), and word processing. His 25 years of experience in writing about science and technology includes a nearly 20-year concentration on PC hardware and software. He also has a proven track record of making technical issues easy for non-technical readers to understand, while holding the interest of more knowledgeable readers. Writing credits include eight computer-related books, major contributions to four others, and more than 2,000 articles in national and worldwide computer and general interest publications. His two most recent books are The Underground Guide to Color Printers (Addison-Wesley, 1996) and Troubleshooting Your PC, (Microsoft Press, 2000, with co-author Alfred Poor).

Much of David's current writing is for PC Magazine, where he has been a frequent contributor since 1983 and a contributing editor since 1987. His work includes feature articles, special projects, reviews, and both hardware and software solutions for PC Magazine's Solutions columns. He also contributes to other magazines, including Wired. As Computers Editor at Science Digest from 1984 until the magazine stopped publication, he wrote both a monthly column and additional articles. His newspaper column on computers appeared in the Newark Star Ledger from 1995 through 1997.

Non-computer-related work includes the Project Data Book for NASA's Upper Atmosphere Research Satellite (written for GE's Astro-Space Division), and magazine articles and AV productions on subjects ranging from cosmology to ape language experiments. David also develops and writes testing scripts for leading computer magazines, including PC Magazine's PC Labs. His scripts have covered a wide range of subjects, including computers, scanners, printers, modems, word processors, fax modems, and communications software. He lives just outside of New York City, and considers himself a New Yorker at heart.


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