Head Crash

A head crash is when one or more of the heads in a Head Stack Assembly (HSA) meets the rotating platter.

Due to the disk spinning very fast, typically at around 7200 rpm, if the heads were to touch the surface, it could cause catastrophic damage. The heads disintegrate due to the intense heat caused by friction, and there would be a scoring mark left behind on the disk surface.

The friction between the slider and the platter also generates a high-pitched whistling noise. This typically occurs on a server hard drive as the bearings wear and the gap between the platter and the head narrows.

Head Stack Assembly

The head stack consists of a number of heads, which interleaves the stack of platters. For a head transplant, the complete stack requires replacing.

The HSA is typically made of aluminium, which is light and non-magnetic.

The Head

People often incorrectly think that the small black slab is the head, but it is actually a slider.

Air Bearing

As the disk spins, air pressure generated under the slider forms an air bearing. The grooves on the slider give it aerodynamic properties so that it flies over the surface of the disk. The slider maintains constant height above the disk surface, which is vital for the proper operation of the read and writes elements of the head. The height is typically in the region of 3 nanometres.

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