Introduction - Hard Disk Drive: Mechatronics and Control - page 7

1.1.3 Small Form Factor Drives
Hard disk drives are designed to be installed inside of a PC, and are produced
in one of few standard sizes and shapes. These standards are called hard disk
form factors and refer primarily to the external dimensions. Compatibility is
the main reason for such standardization of size as well as of the interface used
in the drive. This allows the producers of computing systems to buy HDD
from any manufacturer. There were attempts to make drives smaller than 2 2
inch form factor in mid 1990s. It was not economically viable at that time
as the market was not ready with appropriate application for such storage
devices. Integral Peripheral's 1.8-inch drive and Hewlett Packard's Kittyhawk
(1.3-inch) are two examples of these attempts. The Kittyhawk supported a
capacity of 20 MB on two 1.3-inch disk platters. Recently, IBM introduced
a new product (micro drive)thatuses0.85inchdisks. Thisdrivecanstore
1GBofdataonadiskofthesizeofanAmericanquarter. Theworld's
fi rst gigabyte-capacity disk drive, the IBM 3380, introduced in 1980, was the
size of a refrigerator, weighed approximately 250 kg, and had a price tag of
$40,000. A comparison between the micro drive and IBM 3380 is a proof of
the magnanimity of the achievements that the HDD industry can be proud
of. Now the 2 2 inch format shows promising future with the growing demand
of new applications in the consumer electronics and PDA market. The 3 2
inch drives are still the dominant secondary storage in the server and desktop
applications, where as laptop market is the niche for 2 2 inch drives. Small form
factor drives, such as the micro drive, will provide the storage solutions for the
growing market of PDA, digital entertainment, and other similar products.
1.2 Components of a Hard Disk Drive
Components used in HDD can be broadly classi fi ed into 4 categories - mag-
netic components, mechanical components, electro-mechanical components,
and electronics. The magnetic components, i.e., the media and the head are the
principal components that enables storage and retrieval of binary information.
In HDD, information bits are stored in concentric data tracks on a rotating disk
coated with magnetic media; the information is recorded as well as retrieved
using the read/write head. Practical realization of such non-volatile storage
and retrieval of binary bits, however, involves many other essential compo-
nents, e.g., a motor to spin the disks, an actuator to make read/write head
access the desired data etc. Figure 1.2 shows the important components found
in a typical HDD. Functions and special features of some of these components
are brie fl yexplainedhere.