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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Construction and Operation of the Hard Disk | Hard Disk Head Sliders, Arms and Actuator ]

Head Sliders

Hard disk read/write heads are too small to be used without attaching them to a larger unit. This is especially true of modern hard disk heads. Each hard disk head is therefore mounted to a special device called a head slider or just slider for short. The function of the slider is to physically support the head and hold it in the correct position relative to the platter as the head floats over its surface.

Sliders are given a special shape to allow them to ride precisely over the platter. Usually they are shaped somewhat like a sled; there are two rails or runners on the outside that support the slider at the correct flying height over the surface of the disk, and in the middle the read/write head itself is mounted, possibly on another rail.

As hard disk read/write heads have been shrinking in size, so have the sliders that carry them. The main advantage of using small sliders is that it reduces the weight that must be yanked around the surface of the platters, improving both positioning speed and accuracy. Smaller sliders also have less surface area to potentially contact the surface of the disk.

A graphic illustration of what approximately 15 years' worth of
technological evolution has done to hard disk head sliders.
At left, a slider from a 40 MB 5.25" ferrite-head drive;
at right, the slider from a 3.2 GB, 3.5" MR-head drive.

The hard disk industry has given names to various generations of slider technology. When the design was first reduced to 50% of the size of the first hard disk sliders, someone decided to call it the nano-slider, where "nano" is the prefix denoting "one billionth". Of course the name is silly, since the sliders have not shrunk by even a factor of 10. The newest sliders have been shrunk from the "nano" size by about another 50% and are being called pico-sliders, which in this author's opinion is an equally silly name, and for the same reason. :^)

Each slider is mounted onto a head arm to allow it to be moved over the surface of the platter to which it is mated.

Next: Head Arms


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