Explanation of Hard Disk with its types

1. Presented By
AMZAD KHAN

2. A hard disk drive (HDD), hard disk, hard drive,
or fixed disk is an electro-mechanical data storage
device that stores and retrieves digital
data using magnetic storage and one or more rigid
rapidly rotating platters coated with magnetic
material. The platters are paired with magnetic heads,
usually arranged on a moving actuator arm, which
read and write data to the platter surfaces. Data is
accessed in a random-access manner, meaning that
individual blocks of data can be stored and retrieved
in any order. HDDs are a type of non-volatile storage,
retaining stored data even when powered off.

4.  Platters
The platters are the circular discs inside the hard
drive where the 1s and 0s that make up your files
are stored. Platters are made out of aluminum,
glass or ceramic and have a magnetic surface in
order to permanently store data. On larger hard
drives, several platters are used to increase the
overall capacity of the drive. Data is stored on the
platters in tracks, sectors and cylinders to keep it
organized and easier to find.

5.  The Spindle
The spindle keeps the platters in position and
rotates them as required. The revolutions-per-
minute rating determines how fast data can be
written to and read from the hard drive. A typical
internal desktop drive runs at 7,200 RPM, though
faster and slower speeds are available. The
spindle keeps the platters at a fixed distance apart
from each other to enable the read/write arm to
gain access.

6.  The Read/Write Arm
The read/write arm controls the movement of the
read/write heads, which do the actual reading
and writing on the disk platters by converting the
magnetic surface into an electric current. The arm
makes sure the heads are in the right position
based on the data that needs to be accessed or
written; it's also known as the head arm or
actuator arm. There is typically one read/write
head for every platter side, which floats 3 to 20
millionths of an inch above the platter surface.

7.  Actuator
The actuator or head actuator is a small motor
that takes instructions from the drive's circuit
board to control the movement of the read/write
arm and supervise the transfer of data to and
from the platters. It's responsible for ensuring the
read/write heads are in exactly the right place at
all times.

8.  Other Components
As well as the casing on the outside of the hard
disk that holds all of the components together, the
front-end circuit board controls input and output
signals in tandem with the ports at the end of the
drive. No matter what the type of drive, it has one
port for a power supply and one port for
transferring data and instructions to and from the
rest of the system.

9. Currently, we can group hard drives into four
types:
 Parallel Advanced Technology Attachment
(PATA)
 Serial ATA (SATA)
 Small Computer System Interface (SCSI)
 Solid State Drives (SSD)

10.  These were the first types of hard disk drives to
be developed. They made use of the Parallel
ATA interface standard to connect to
computers.
 These types of drives are the ones we refer to as
Integrated Drive Electronics (IDE) and
Enhanced Integrated Drive Electronics (EIDE)
drives
 Data transfer rate can go up to 133MB/s and a
maximum of 2 devices can be connected to a
drive channel. Most of the motherboards have
a provision of two channels, thus a total of 4
EIDE devices can be connected internally.

11.  They make use of a 40 or 80 wire ribbon cable
transferring multiple bits of data
simultaneously in parallel. These drives store
data by the use of magnetism.

12.  These hard drives have replaced the PATA drives in desktop
and laptop computers. The main physical difference between
the two is the interface.
 When buying a disk drive, you need to know its storage
capacity and how much storage you want.
 SATA drives can transfer data faster than PATA types by using
serial signaling technology.
 SATA cables are thinner and more flexible than PATA cables.
 They have a 7-pin data connection, with a cable limit of 1
meter.
 Disks do not share bandwidth because there is only one disk
drive allowed per SATA controller chip on the computer
motherboard.
 They consume less power. They only require 250 mV as
opposed to 5V for PATA.

14.  These are quite similar to IDE hard drives but
they make use of the Small Computer System
Interface to connect to the computer.
 SCSI is a set of standards for physically
connecting and transferring data between
computers and peripheral devices. These
standards define commands, protocols,
electrical, optical and logical interfaces.

15.  SCSI drives can be connected internally or
externally. Devices that are connected in a SCSI
have to be terminated at the end. Here are
some of their advantages.
 They are faster.
 They are very reliable.
 Good for 24/7 operations.
 Have better scalability and flexibility in arrays.
 Well-adapted for storing and moving large
amounts of data.

17.  These are the latest in drive technology that we
have in the computer industry. They are totally
different from the other drives in that they do
not consist of moving parts.
 They also do not store data using magnetism.
Instead, they make use of flash memory
technology. They make use of integrated
circuits or semiconductor devices to store data
permanently, at least until it is erased.

18.  Faster data access.
 Less susceptible to shock.
 Lower access times and latency.
 Durability.
 Less power usage.