Hard Drive Problems

Head Crash

Whilst the term "crash" is synonymous with any failure of a computer system or attached device, in the context of a hard drive, the meaning is specific and means a lot more than just the hard drive has stopped working.

A hard drive crash is where the read/write heads in the drive, contact the recorded surface of the disk platter and cause physical damage. This is caused by a failure of the heads to "float" across the disk surface and can be caused by events as diverse as impact, contamination and physical mechanical wear.

Whatever the cause the end result is the same, there is damage to the disk, data will no longer be accessible, and hard disk data recovery is the only option if data is required.

Crash damage is usually localised in a radial position, once it has happened the disk will fail and cease operation, so there should not be further damage. There is a risk that repeated attempts to restart the disk could cause additional damage as the read heads have probably been damaged, and the surface of the disk will no longer be smooth resulting in areas where the aerodynamic effects that allow the heads to float over the surface fail and further impacts occur.

[Click here for help]

---

Symptoms

The symptoms of a head crash are identical to those presented by other failures, there is not normally any significant loud noise, so you might thing there has been a crash but there could be some other failure.

Typically, once a disk has suffered crash damage, the only noise from the disk will be a steady clicking. This is the disk attempting to access data by repositioning the read/write heads and re-trying. These symptoms are identical to those presented by alignment failure and certain electronic/memory problems. The drive has no means of knowing that a crash has taken place, only that it is not receiving the expected data via its read channel.

What can be done?

Even following some quite severe crash damage there will be large areas of the disk platter that are in pretty good condition, giving a chance for the recovery of data from the disk.

The disk read/write heads will also have been damaged by the impact and so data recovery will, in almost all instances, involve head replacement before any data can be accessed.

The critical factor in determining whether a hard disk recovery is viable is the location of the damage. Damage in the data area of the disk will mean the some files cannot be recovered intact but the recovery process can avoid those areas and concentrate on the undamaged ones. If the data that you need is stored away from the damaged portion of the disk then it will be recovered.

The problems caused by a head crash often affect the areas of the disk used for storing critical drive information, such as defect lists and firmware logs, or in frequently accessed areas of the file system containing the file allocation data. If these are destroyed the chances of a successful recovery of any meaningful data significantly reduced, however recovery of your critical data may still be achievable.