Computer Technicians 203: Hard Disk Failures

Record scratches, clicks, crashes and burnouts

Although the above three error categories can wreak havoc by themselves, these final categories are every user’s fear and every technician’s worst nightmare. Most of the time, we don’t even notice our hard-drives running because of how closed they are and the fluid bearings that make all movement relatively silent. Therefore, if you hear a click in the general vincinity of the drive, it means that it might’ve sustained a head crash. A head crash occurs if the read-write head, which hovers a couple of microns above the platter on a buffer of air suddenly loses the air layer that keeps it hovering and impacts the platter itself. Normally, the heads only touch the platter on the so-called landing zone (LZ), literally a parking zone for the drive head during shutdown – however, should this happen on a formatted and occupied sector, several things happen. First off, it can be caused by anything from a dust particle kicking the head out of alignment to an actuator failure. The drive head falls down, scrapes off part of the protective disk coating and literally scratches the disk surface – not on one point, but along a line, as the drive can be spinning up to 10krpm. On top of that, it can generate more particles which can worsen the effect exponentially. The sounds emitted from a head-crashed drive can range from a series of clicks to a whirr that sounds like a small drill bit – either way, hearing one of those is really bad news because you can’t repair it, and you have slim chances of backing up what’s still there without encountering the bad sector again.

Circuit burnouts are another horror that awaits some disks, and it’s usually fatal, because it’s prompted by either a fault in the power supply, or a lightning strike that fried the circuitry. Some people suggest that even a burned-out circuit board can be fixed, usually by swapping it with an exact version from another, preferably busted, drive. However, in some cases a specific drive can need a specific drive, and even swapping with another drive’s circuitry may render it inoperable. In other cases, depending on the current that actually went through the drive, the disk platters might get degaussed (completely demagnetized) in which case you’re looking at a blank and unrecoverable disk. Sometimes, the circuitry does indeed help, though, so if you have faith in your ability and a bit of luck on your side (a horseshoe would help, unless you tacked it right onto the comuter chassis), you can attempt it.

The remedy

Obviously, the best remedy for all hard-drive failures is making backups often. Nothing can make your data as safe as making backups – if you can afford it, an external hard-drive in a properly closed enclosure can keep it relatively safe, and so can a decent brand of DVDs and a good DVD-writer – you can literally back up your entire drive in 2 hours with a single DVD spindle if need arise. For all the lighter errors, the remedies have already been listed – running CHKDSK can, in theory, single out all the bad sectors and transport data to safer regions, and cables are simple to reseat. Should a fatal error occur, like a circuit burnout or a disk crash, usually nothing can be done. Data recovery might be possible, but you’ll have to shell out a lot for it – possibly more than your data is worth to you. Our articles on Performing data recovery and TNCT-102 might give you an insight into what tools might be able to salvage your drives, but be prepared for the fact that any major error usually spelled doom for the drive, and that you’ll need to shell out for a replacement.

 
Written by Boris M