13.1 through 13.5, 13.10 and 13.11

Chapter 13 Disk Storage, Basic File Structures, and Hashingsided ifboth surfaces are used. To increase storage capacity, disks are assernbled intoa disk pack, as shown in Figure 13.1(b), which may include many disks and thereforernany surfaces. Information is stored on a disk surface in concentric circles ofsrnoll width,a each having a distinct diarneter. Each circle is called a track. In diskpacks, tracks with the same diameter on the various surfaces are called a cylinderbecause of the shape they would form if connected iu space. The concept of a cylinderis important because data stored on one cylinder can be retrieved much fasterthan if it were distributed among different cylinders.The number of tracks on a disk ranges from a few hundred to a few thousand, anclthe capacity of each track typically ranges from tens of Kbytes to 150 Kbytes.Because a track usually contailrs a large amount of information, it is divided intosmaller blocks or sectors. The division of a track into sectors is hard-coded on thcdisk surface and cannot be changed. One type of sector organization, as shown inFigure 13.1(a) A single-sided disk with readlwrite hardware, (b) A disk pack with readlwrite hardware(a)lIActuatort IIArmRead/writeneao Spindle Disk rotation(b)Cylinderof tracks(imaginary)4, In some disks, the c rcles are now connected into a k nd of continuous spiral