Hard Disk Drive Design and Technology

Magnetic Hard Disk Drive (page 4)

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In order to keep the magnetic head as close to the disk surface as possible, a self-pressurized air-bearing design is used for the sliders (see figure on the right).

For the CSS drives, the slider rests on the landing zone of the disk when the power is off. When the drive is turned on, the disk starts spinning and air pressure builds up between the slider and the disk. Eventually, the slider starts flying at the altitude (called the flying height) of a few dozen nanometers.

To get a feeling for what "a few nanometers" mean, lets remember that a human hair is about 30 microns in diameter (1 micron = 1,000 nm). An average bacteria can be typically a few hundred nanometers in size.

Using some imagination, the following example could be also used as an illustration:

If the slider / disk interface of the modern magnetic hard drive is scaled up to the extent that the slider becomes as long as a Boeing 747 jumbo-jet , then the following amazing picture (on the left) will appear:

Our slider-airplane will fly at the altitude of only a few mm at the speed of approximately 65 mph periodically landing on its belly and taking off again about 50,000 times. And still the surface the airport, which consists of a few mm-thick layers will stay intact for years...

It may not sound realistic, but this is how things really are inside the hard disk drive. Plus, both the airplane and the airport will never be serviced or repaired... Finally, all this incredible technology does not cost millions, but just a few hundred dollars!

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