Physical Characteristics of Disks1.The storage capacity of a single disk ranges from 10MB to 10GB. A typical commercial database may require hundreds of disks. 2.Figure 10.2 shows a moving-head disk mechanism. oEach disk platterhas a flat circular shape. Its two surfaces are covered with a magnetic material and information is recorded on the surfaces. The platter of hard disksare made from rigid metal or glass, while floppy disks are made from flexible material. oThe disk surface is logically divided into tracks, which are subdivided into sectors. A sector (varying from 32 bytes to 4096 bytes, usually 512 bytes) is the smallest unit of information that can be read from or written to disk. There are 4-32 sectors per track and 20-1500 tracks per disk surface. oThe armcan be positioned over any one of the tracks. oThe platteris spun at high speed. oTo read information, the arm is positionedover the correct track.
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Hard disk drive, disk, Cylinder-head-sector, Rotating disc computer storage media