By Mirza Danial Masood BS(IT) Department, U.O.S M.B.Din

HARD DISK

Hard Disk It is a storage device that used magnetically

platters to store data, instruction and information.

The Desktop and notebook computer contains 1 or more hard disks.

It have storage capacity from 40 GB to 1.5 TB and more.

A Hard Disk that is mounted inside the system unit sometimes is called fixed-disk.

Hard DiskA Hard Disk which can remove the medium

from one computer and carry it to another computer is called Portable-disk.

Hard Disk store data by two ways: Longitudinal Recording . Perpendicular Recording .

Longitudinal Recording Hard disks stored data using, longitudinal

recording , which aligned the magnetic particles horizontally around the surface of the disk.

Perpendicular Recording Hard disks stored data using, perpendicular

recording , which aligned the magnetic particles vertically or perpendicular around the surface of the disk .

Components of Hard DiskThese are some components of hard disk : Platters . Disk case. Read/Write Head . Cylinder . Spindle . Disk cache .

Components of Hard Disk Platter : It is a circular, metal disk that is

mounted inside a hard disk drive. It is made of aluminum, glass, or ceramic and is coated with an alloy material that allows items to be recorded magnetically on its surface.

Before writing data , the hard disk must be formatted .

Components of Hard DiskThe process of dividing the disk into tracks

and sectors , so that the operating system can store and locate data and information on the disk is called Formatting .

A narrow recording band that forms a full circle on the surface of the disk is called Track.

The disk’s storage locations consist of pie-shaped sections, which break the racks into small arcs called sectors .

Components of Hard Disk The smallest unit of disk space that stores

data and information is called Cluster .

Components of Hard Disk Disk Case : The rectangular shaped disk case

holds all of the components of a hard disk drive . Read/Write Head : A read/write head is the mechanism that reads items and writes items in the drive as it barely touches the

disk’s recording surface .

Components of Hard Disk

Cylinder :A cylinder is the vertical section of a track that passes through all platters .

Components of Hard Disk

Components of Hard DiskSpindle : The spindle holds the platters

together and the motor rotates the plattersat their designated speed, which is measured in RPM.

The platters in the hard disk rotate at a high rate of speed. This spinning, which usually is 5,400 to 15,000 revolutions per minute (rpm) .

Components of Hard Disk

Disk cache : sometimes called a buffer, consists of a memory chip(s) on a hard disk

that stores frequently accessed items such as data, instructions, and information .

Head CrashA head crash occurs when a read/write head

touches the surface of a platter, usually resulting in a loss of data or sometimes loss of the entire disk. Dirt, hair, dust, smoke, and other particles could cause the hard disk to have a head crash .