Head crash may be the two most devastating words a computer owner will ever hear, and for good reason. It is one of the ways the hard drive of a computer can physically fail. The read/write head of a hard drive is meant to fly above the spinning data-storage platter below, separated by a gap smaller than a single particle of dust. The gap itself is crucial, as any physical contact between the head and the platter will cause extensive damage to the delicate magnetic storage media. Depending on the severity of the crash, some or all of the data stored on the drive will be lost.
A head crash can be caused by the read/write head striking dust or debris on the surface of the platter. One of the most common causes is vibrating or dropping the computer while in use. A crash can also be caused by the mechanical failure of other components of the hard drive, and by electrical surges. Newer models of hard drives have been built with active hard disk protection, a system that uses a motion sensor to detect acceleration. If the protection system is triggered, it will park the drive to protect against physical damage.
When a head crash occurs, the physical contact between the head and the platter will score the surface of the platter. Platters spin at a very high speed, and the damage from even brief contact with the head can be extensive. The scoring destroys the data in that sector, and also releases electromagnetic dust. This dust has the potential to set off a chain reaction of continued crashes if the drive is left in operation.
The crash itself is typically accompanied by a high-pitched grinding or screeching sound. There may also be a repeated clicking noise, popularly known as the click of death, which is the sound of the head hitting a limiter as the drive attempts to recalibrate. Computers that have been making these types of noises should be taken to a professional repair facility, as attempting to restart them can cause additional damage and data loss.
It may be possible to recover some of the data on a disk following a head crash, but only with the assistance of a data recovery expert. The data in the immediate contact zone have been irretrievably lost. Depending on the areas of the drive damaged, data recovery from other sectors of the disk may or may not be possible. A clean-room setup is required in order to provide a sterile environment for working on the internal components of a hard drive. This type of data recovery is not a project that can be done at home.
The causes of a head crash aren’t always preventable, and they can occur without warning. Experts recommend regularly backing up a hard drive to an external device or to an online backup service. Installing a new hard drive and restoring from backup is quicker, easier, and cheaper than attempting to recover data from a head crash, provided a backup is available. The services of a data recovery expert can be expensive, and the results are not guaranteed.