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2. Number of tracks per surface,
3. Number of sectors per track, and 4. Number of bytes per sector
It is a multiple of the above four parameters. That is,
Storage capacity of a disk system = Number of recording surfaces
x Number of tracks per surface
x Number of sectors per track
x Number of bytes per sector
For example, suppose a disk pack has 10 disk plates each having 2655 tracks. Suppose
there are 125 sectors per track, and each sector can store 512 bytes. Since the disk pack
has 10 disk plates, so it will have 18 recording surfaces (excluding the upper surface of
the topmost disk and the lower surface of the bottommost disk). Hence the capacity of
this disk pack will be = 18 x 2655 x 125 x 512 = 3,05,85,60,000 bytes = 3 x 10 9 bytes
(approximately) = 3 GB (3 Giga Bytes). Essentially one character can be stored per byte.
So a disk system with 3 GB capacity can store 3 billion characters of information.
Notice that the more recording surfaces a particular disk system has, the greater its
storage capacity will be. For example, in case of a disk system having only one disk (i.e.,
a floppy disk), the storage capacity of a double-sided disk plate will be about twice that
of a single-sided one. And the storage capacity of a disk system having multiple disk
plates (i.e., a disk pack) will be many times more than a single-disk system.
As the storage capacity of a disk system is also directly proportional to the number of
tracks per surface, disks having larger diameter can have more tracks and larger storage
capacity. However, disk size cannot be made too large because it will affect the overall
size of the disk unit. And the constant effort of the designers of disk systems is to provide
more storage capacity in as compact form as possible. Hence instead of increasing the
disk size for larger storage capacity, the designers prefer to increase the storage capacity
by increasing th& tracks per inch of surface and bits per inch of track. That is, a constant
goal of the designer...
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This document was uploaded on 04/07/2014.
- Spring '14