... only run at 3600 to 5200 rpm. Today's ones can run 7600 to 10000 rpm. There is a layer of magnetic material on the surface of the platters. Today a thin-film media is used here. Thin-film media is a microscopic layer of pure metal bonded to the substrate surface through an interim layer. Because the distance between head and platters is very small (about 10 micro inches), but they can not touch with each other. So the thin-film media is very flat and is coated with a protective layer to help survive head crashing. 2. the arm and read and write head The arm that holds the read/write heads is controlled by the mechanism in the upper-left corner, and is able to move the heads from the hub to the edge of the drive. The arm and its movement mechanism are extremely light and fast. The arm on a typical hard-disk ...

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