We have to mount a magnetic disk on a disk drive for reading/writing of data from/to it. A disk drive contains all mechanical, electrical, and electronic components for holding one or more disks and for reading/writing of data from/to it. It contains a central shaft on which the disks are mounted, an access arms assembly, a set of read/write heads, and motors to rotate the disks and move the access arms assembly. although, disk drives vary greatly in their shape, size, and disk-formatting pattern, we classify them broadly into two types:
Disk drives with interchangeable disks. These disk drives allow loading and use of different disks in the same disk drive at different instances, enabling off-line storage of data on disks. They provide virtually unlimited capacity to a disk system because as many disks as required can be used one after another to store very data sets.
Disk drives with fixed disks. These drives come along with a set of permanently fixed disks. The disks, read/write heads, and access mechanisms of the disk drive are housed permanently in a sealed, contamination-free container. Sealed packaging allows the disks to operate in a dust-free environment. This enables designers to provide increased data density (by using smaller magnetized spots) on each square inch of disk surface by reducing the distance between a read/write head and its corresponding disk surface. Hence, as compared to disk drives with interchangeable disks, these drives provide larger storage capacity with same size disks and same number of disk surfaces. However, the disks are not removable from their disk because of sealed packing. Thus, storage capacity of these disk systems is limited.