Report about: Hard disk drive

Prepared by:

Azadi Taib Toreen dilshad

Aram Hady Ava Usman

Ashty Jihad Awat Ahmad

Sponsored by:Shadan
Contents
History:..............................................................................................................3
How hard drive works?.....................................................................................3
Hard drive physical component........................................................................4
PLATTERS:.........................................................................................................4
THE SUBSTRATE MATERIAL:.............................................................................5
MEDIA LAYER:...................................................................................................6
PROTECTIVE LAYER:..........................................................................................6
PLATTER DIVISIONS:..........................................................................................6
TRACKS:.............................................................................................................6
SECTORS:...........................................................................................................7
CLUSTERS:.........................................................................................................7
READ/WRITE HEADS:........................................................................................7
THE SPINDLE MOTOR:.......................................................................................8
HARD DISK LOGIC BOARD:................................................................................8
DRIVE BAY:........................................................................................................9

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History:
Hard disk drives were introduced in 1956 as data storage for an IBM
real time transaction processing computer and were developed for use
with general purpose mainframe and mini computers. The first IBM
drive, the 350 RAMAC, was approximately the size of two refrigerators
and stored 5 million 6-bit. Characters (the equivalent of 3.75 million 8-
bit bytes) on a stack of 50 discs

How hard drive works?

A hard disk is a sealed unit containing a number of platters in a stack.
Hard disks may be mounted in a horizontal or a vertical position. In this
description, the hard drive is mounted horizontally.Electromagnetic
read/write heads are positioned above and below each platter. As the
platters spin, the drive heads move in toward the center surface and out
toward the edge. In this way, the drive heads can reach the entire surface
of each platter.

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Hard drive physical component
PLATTERS: 
Platter is a circular, metal disk that is mounted inside a hard disk drive.
Several platters are mounted on a fixed spindle motor to create more
data storage surfaces in a smaller area. The platter has a core made up
of aluminum or glass substrate, covered with a thin layer of Ferric oxide
or cobalt alloy. On both sides of the substrate material, a thin coating is
deposited by a special manufacturing technique. This, thin coating where
actual data is stored is the media layer.

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When the magnetic media is applied to the surface of the substrate
material, a thin lubricating layer is applied to protect the material. This
complex three layered media is discussed in detail as follows:

THE SUBSTRATE MATERIAL: 

The bulk material of which platters are made up, forms the base on
which media layer is deposited. The substrate has no specific function
but to support the media layer. The most commonly used material for
making this physical layer is an Aluminum alloy. This alloy is rigid,
lightweight, stable, inexpensive, easy to work with and is readily
available. Earlier, since the gap between the heads and the platter was
relatively high
the platter surface being smooth and flat was less of an issue. However,
as technology advances, the gap between heads and platters is decreasing
and the speed that the platters spin at is increasing. For this reason
demand for alternatives on the platter material are increasing. Glass
platters are replacing aluminum platters because they provide improved
rigidity, better quality, thinner platters, and thermal stability.

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MEDIA LAYER:
The substrate material forms the base upon which actual recording
media is deposited. The media layer is a thin coating of magnetic
material applied to the surface of the platters and where the actual data
is stored. Its thickness is only a few millionths of an inch. Special
techniques are employed for the deposition of magnetic material on the
substrate material. A thin coating is deposited on both sides of the
substrate,
mostly by vacuum deposition process called magnetron sputtering.
Another such method is electroplating, using a process similar to that
used in electroplating jewelry.

PROTECTIVE LAYER:
On the top of the magnetic media, is applied a super-thin, protective,
lubricating layer. This layer is called the protective layer because it
protects the disk from damage caused by accidental contact from the
heads, “head crash” or other foreign material from entering the drive

PLATTER DIVISIONS: 
In order to get maintain the organized storage and retrieval of data the
platters are organized into specific structures. These specific structures
include tracks, sectors, and clusters.

TRACKS: 
Each platter is broken into thousands of tightly packed concentric
circles, known as tracks. These tracks resemble the structure of annual
rings of a tree. All the information stored on the hard disk is recorded in
tracks. Starting from zero at the outer side of the platter, the number of
tracks goes on increasing to the inner side. Each track can hold a large
amount of data counting to thousands of bytes.

SECTORS: 
Each track is further broken down into smaller units called sectors. As
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sector is the basic unit of data storage on a hard disk. A single track
typically can have thousands of sectors and each sector can hold more
than 512 bytes of data. A few additional bytes are required for control
structures and error detection and correction.

CLUSTERS: 
Sectors are often grouped together to form Clusters.

READ/WRITE HEADS: 
The heads are an interface between the magnetic media where the data is
stored and electronic components in the hard disk. The heads convert
the information, which is in the form of bits to magnetic pulses when it is
to be stored on the platter and reverses the process while reading.

The heads are the most sophisticated part of the hard disk. Each platter
has two read/write heads, one mounted on the top and the other one at
the bottom. These heads are mounted on head sliders, which are
suspended at the ends of head arms. The head arms are all fused into a
singular structure called actuator, which is responsible for their
movement.

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THE SPINDLE MOTOR: 
Spindle motor plays an important role in hard drive operation by
turning the hard disk platters. A spindle motor must provide stable,
reliable, and consistent turning power for many hours of continuous use.
Many hard drive failures occur due to spindle motor not functioning
properly

HARD DISK LOGIC BOARD:

Hard disk is made with an intelligent circuit board integrated into the
hard disk unit. It is mounted on the bottom of the base casting exposed to
the outer side. The read/write heads are linked to the logic board
through a flexible ribbon cable.

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DRIVE BAY: 
The entire hard disk is mounted in an enclosure designed to protect it
from the outside air. It is necessary to keep the internal environment of
the hard disk free of dust and other contaminants. These contaminants
may get accumulated in the gap between the read/write heads and the
platters, which usually leads to head crashes.

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The bottom of the disk is also called base casting. The drive mechanics
are placed in the base casting and a cover, usually made up of aluminum
is placed on top to enclose heads and platters. The entire contents placed
on the base and cover chamber are collectively known as the head-disk
assembly .
Once this assembly is opened, it would instantly contaminate the

contents and eventually ruin the drive. On the bottom of the base

casting is present the logic board, which is separated from the base

casting using a cushioning material.

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