>I've managed hundreds of disk problems, of which only a handful were >hardware problems:
I've seen lots of hardware problems, BUT, it should be noted that I also have worked with potentially thousands of drives, many of which are in excess of 10 years old and have been well abused. When I see hardware problems, it is usually one of 3 things (in order that I see them): 1. Drive fails to spin up from a dead (or dying) motor. That is the single most common hardware failure I see. Next would be 2. Head "stiction". That is when the heads either adhere to the drive platters due to years of grime built up inside (even assembled in a clean room, gunk will still make it into the drive and it WILL build up on the heads as they spin). When the drive is off and cools down, this normally harmless gunk becomes a mild glue, and literally glues the heads to the platter. Sometimes this can be cured by tapping the drive to unstick it, other times its a loss. I also lump into this category failed head stepper motors. Although technically it is a different fault, I count it with the stuck heads because in many cases stiction is what causes the stepper motor to burn out. And finally 3: Controller failure. The smarts on the drive die. Usually a fried chip or other part. IF you have an identical drive, you can usually swap out the controller board to revive the drive. However, you have to know that it is really the exact same drive. Its not uncommon for a company to go thru different revisions of a drive during a drive's line life. It is not always safe to swap the controller from a different revision. With all the drives I've dealt with, I've only ever seen a handful of truly crashed heads (where the head either hits the platter, and/or is ripped off the arm). The few times I've seen it, you usually know it as it makes a pretty loud grinding noise (as would be expected, since you are now dragging metal on metal at a few thousand RPM). And beyond all the hardware failures I have seen, I have seen far more media failures. Technically they can be lumped into hardware as well, since the drive platters are technically hardware. However, since mild media failures can be corrected with software, I prefer to consider them software failures. As a drive ages, the magnetic media on the platters starts to fail. Its just physics. Magnetism will NOT last forever. As it decays, the drive becomes more and more unreliable. Eventually enough bad sectors crop up that the drive is no good. Also, finding bad sectors in a drive out of the blue is usually a sign that the media is starting to fail. Sometimes its a random occurrence and the drive will continue to operate fine for years and years to come... other times it is just the beginning of a cascade failure, and more sectors will die out very shortly. And of course, the #1 thing I have found wrong with drives is just simply corrupted data. These are 100% software related. Usually due to constant system crashing, and the computer writing out incorrect data at the wrong place and wrong time. These can be anywhere from the relatively harmless things like bad file dates, thru slightly worse things like bad drive tables, thru the really bad things like totally corrupted formats. These are all almost always 100% fixable in terms of reusing the drive. A new format will almost always correct the problem (I hesitate to say will always correct it, as as soon as I do, someone will come up with an instance that says I'm wrong... but I've personally never lost a drive to this kind of failure). However, even though the drive can be saved, it doesn't always mean you can save the data off the drive. Sometimes it is lost beyond what any commercially available tools can get at. But a software failure is almost always trivial for a professional recovery shop to salvage. (and it getting better and better at the home user being able to do it as well as better and better tools are being sold to do it). Not sure anyone cared, but since I'm trying to avoid doing a long, boring, complicated job here at work, I figured I'd waste some time and chime in with my experiences. -chris <http://www.mythtech.net> ___________________________________________________________________________ To unsubscribe send a mail message with a SUBJECT line of "unsubscribe" to <[EMAIL PROTECTED]> or <[EMAIL PROTECTED]>
