It is the media upon which the magnetic data is stored. Often platters are made of an aluminum alloy, however IBM is opting for glass platters as it offers better thermal stability.

    The media layer is a very thin coating of magnetic material, which is applied by either using the electroplating or sputtering method, it is typically only a few millionths of a centimeter in thickness; upon which the data is stored.

    Data are recorded in a form of a thin magnetic patterns on the platters surface's; the bulk of the material of the platter is called the substrate and does nothing but support the media layer.

    Each platter has two surfaces capable of holding data; each surface is read/written by a single head floating just above it. Often both surfaces of each platter are used, but not always. The platters are juxtaposed so that they form an overlaying of parallel layers each spinning at a rate of at least 150 mph!

    Multi plattered drives are more sophisticated to devise than those with a single platter, due to the extra stress added on the spindle by the added weight of the extra platter/s. Subsequently, weight, noise and vibration strongly influences the design aspects of the hard drives.