Let's have a quick look at your hard drive - that mysterious doodad that sits inside the case of your computer, whirring and occasionally chuckling quietly to itself, and storing massive amounts of program code - and probably all of your correspondence and data files. It's a high-precision piece of machinery, and actually very delicate; and like all equipment in that category, there are only two kinds: those that HAVE worn out, and those that WILL wear out. It's only a question of time before your hard drive dies. Years, if you're lucky (and reasonably careful)....

Here's why. Your hard drive is a small stack of metal discs (usually called "platters") mounted in a sealed case. The whole stack is constantly spinning at 3600 rpm, or even faster in some drives. (Run your car engine that fast in top gear, and you'll be doing better than 100 kph!) Each platter is coated on both sides with a very thin, brittle, highly polished layer of a magnetic medium somewhat comparable to the dark brown stuff on your favourite audio cassette tape. When the drive is running, a tiny magnetic head floats just off the surface of each platter on a cushion of air about a tenth of the thickness of a human hair. This head reads and writes the data you want to store. It writes a track which may be narrower than a thousandth of an inch on some drives -- compare that to the tape head on your audio cassette deck, which writes a track that may be 50 times wider than the data track on your hard drive. You can see that a hard drive really is a high-precision piece of machinery. It's also amazingly fast. Consider this: That tiny little head has to find the right track (out of several hundred on that face of the platter), and position itself exactly over that tiny little track, before it can read or write any data - and it will do all this in a few thousandths of a second. Then it has to keep itself exactly in the right place while you bump the desk and pound on your keyboard.

Amazing little gizmo, isn't it? The precision and speed involved boggles my mind - it's a wonder hard drives work at all, much less as reliably as they do. BUT THEY DON'T WORK FOREVER! It probably will be years before your drive quits on you - but it will die some day. How much of your data will be recoverable will depend on what wore out first - but you'll lose something, and maybe everything on it, when your hard drive dies. And there is nothing you can do to prevent or delay its happening.

What's worse is that the hard drive is the one component of your computer which is absolutely essential to the recovery of your data. If any other component dies, you can take the hard drive out of your computer and put it in another, and recover your data that way. But when your hard drive dies, your data usually goes with it.

Hard drives can die unnatural deaths too. If you bump the case of your computer hard enough while the hard drive is running, it may jolt a head into contact with its platter. (Remember how thin that air cushion is? And how fast the platter is spinning?) It's called a "head crash" for very good reason, and the result is usually expensive: an irreparable gouge in the magnetic medium. The section of any file that was written on the disc where the gouge appeared is probably history. And where do the the little chips go that were gouged out of the surface of the platter by the head crash? Well, they're still flying around in there - it's a sealed case, remember? Every time one of those chips gets sucked under a head, it causes more damage, and your hard drive dies an early and ugly death.

Your backups aren't up to date? Too bad - because your data and program files on that drive are probably toast, unless you can copy them off that drive real quick. But, that's what backups are all about. Uh - you HAVE been doing them, haven't you?
 

Rob Mayhew
Vancouver, B.C.

copyright 1991
 

A version of this article was published in the December, 1992 issue of The Computer Paper (B.C. edition).