Hard Disks: Still
the major secondary-storage device for
desktop/tower computers.
•Thin, rigid metal, glass, or ceramic
platters covered with a substance that allows data to be held in the form of
magnetized spots.
•The more platters there are, the higher
the drive capacity.
•Store data in tracks, sectors, and clusters.
•Formatting creates a file allocation
table that maps files to clusters.
•Drive heads ride on .000001” cushion of
air, and can crash!
•Important data should always be backed
up!
•Hard Disk Types:
•Nonremovable hard disk –
Also known
as a fixed disk; is
housed in the microcomputer system unit
and is used to store nearly all programs and most
data files. Usually
consists of several metallic or glass platters,
from 1 to 5.25 inches (most commonly 3.5
inches) in diameter, stacked on
a spindle, with data stored on both sides. Read/write
heads, one for each side of each platter, are
mounted on an access arm that
moves back and forth to the right location on the platter.
•External hard
disk
– Freestanding
disk drive
(portable); usually connected via USB.
•RAID –
redundant array of independent disks; for large computer systems.
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