#HD's go bad
Most drives (the new ones, at least) are meant to work flawlessly for at least
250,000 continuos hours (about 28 years – I guess we have to wait that long to
prove it). I have a [ridiculous] number of [large] drives running, some for as
long as 8 years, and very rarely have a problem. The two times I remember, the
problems were rather induced (shock and vibration).
Most problems I see are software problems and not physical problems. This is
the vast majority of zombie disks out there (they aren't really dead). I mean
by software problems those caused by bogus data recorded in important tracks.
Physical problems are actual media defects, head alignments, etc. These are,
for the most part, much rarer.
Media defect comes to you from factory. It's pretty damn difficult to cause a
media defect (unless you have the custom of opening disk drives with craw
bars). Head alignments are the most common but also the easiest to avoid.
Simply don't ever, ever move a hard disk while spinning. A simple knock on a
computer chassis could cause problems if you get it while the head is tracking
a disk turning 7,000 rpm. Dropping a spinning disk from as little as one inch
will most certainly trash a disk beyond repair. Overheating "might" cause
problems. If it gets too hot, the expansion might be enough to get the head too
close to the media. If that happens, you end up with bogus data recorded (not a
"dead" disk, just zombie). In the worse case, you could end up with a
misaligned head assembly (simple to fix with proper tools – certainly not at
home).
Low level formatting fixes a great majority of zombie disks. These new, large
format, SCSI disks need special tools for low level format. I would not suggest
people afraid of the DOS prompt trying it (at least until Mr.
Look-it's-me-Norton-the-ego comes up with a more pseudo-friendly user
interface, which I doubt it as they would lose their data restoring business).
By restoring just vital disk portions such as partition and boot areas, you
will, most of the time, be able to restore all data. The problem is only
hopeless when the entire disk has bogus data recorded (rare).
By the way, someone said "DOS" isn't ready for large drives. Bull Shit. For
that matter Irix ain't either as I have had more crashes with it than I had
with DOS. DOS' problem is that it has no memory protection which would allow
programs to trash system memory and therefore, could cause bogus data be
written to disk. This is indeed a problem but for 1G disks and 160 kb, single
sided floppies just as well. It has nothing to do with the size of the disk. It
just happens that you get a lot more pissed losing 1G of data than a floppy.
If a important track goes to wallah wallah land, such as track 0, there are no
tools a mortal would have that will fix it. What you might try is to check the
manufacturer BBS or FTP site and look for low level tools. Some, like NEC, DEC,
and Seagate have them available. Sometimes it is necessary to reprogram the
disk itself (download a new track information to track 0). These programs are,
for the most part, Greg pardon me, Greek. But face it, the disk is trashed,
ain't it? Unless you have data you want restored. In that case, stay away from
those tools and seek help. Just ask Greg how it is to low level format a 9gig
Seagate monster (ducking and running away…)