SECONDARY STORAGEby group secondary123

STORAGEAn essential feature of every computer is the ability to save, or store, information

random-access memory (RAM) hard-disk

• holds or store programs that the CPU is currently processing

• provides temporary/ volatile storage

• it loses its contents when power is disrupted

• more storage capacity• provides permanent/

nonvolatile storage• retains data and

information after the computer system is turned off

PRIMARY STORAGE (RAM)

SECONDARY STORAGE

Mechanism of secondary storage

WRITING : process of saving information to secondary storage devices

READING : process of accessing information from secondary storage devices

Characteristics of secondary storage

• MEDIA : actual physical material that retains data & programs

• CAPACITY : how much a particular storage medium can hold

• STORAGE DEVICES : hardware that reads & writes to storage media

• ACCESS SPEED : time required to retrieve data from a secondary storage device

HARD DISKS• use rigid metallic platters that

provide a large amount of capacity• store data & programs by altering

the electromagnetic charges on platter’s surface

• organize files according to :1. tracks – concentric rings without

visible grooves2. sectors – wedge-shaped sections3. cylinders – run through each

stack of platters4. density – how tightly

electromagnetic charges can be packed next to one another

head crash

• occurs when the hard disk makes contact with the drive’s read/write heads

TYPES OF HARD DISKS

INTERNAL• located within the system

unit• used to store programs and

data files• able to store and retrieve

large quantities of information quickly

• provide fast access• fixed amount of storage

EXTERNAL• removable• use the same basic

technology as internal disks• useful to protect or secure

sensitive information• provide additional hard-disk

capacity• use for backing up contents

of internal hard disk

PERFORMANCE ENHANCEMENTS

DISK CACHING- provides temporary high-speed holding area between secondary storage device & CPU

RAID (redundant array of inexpensive disks)- several inexpensive hard-disk drives are connected together

FILE COMPRESSION & DECOMPRESSION- files compressed before storing and decompressed before used

OPTICAL DISCS

Compact Disc

Digital Versatile

Disc

Blu-ray Disc

COMPACT DISC

Known as CD drives which were standard on many microcomputer system.

CD drive can store from 650 MB to 1 GB of data on one side of a CD.

Three basic type of CDs: 1.Read only=CD-ROM 2.Write once=CD-R 3.Rewritetable=CD-RW

Read only=CR-ROM

• Compact disc-read-only-memory

• Used to distribute large database and reference

• Used to distribute large software application packages

Write once=CD-R

• CD-recordable

• Can be written to once

• Used to archive data and to record music downloaded from the Internet

Rewritable=CD-RW

• Erasable optical disc

• The disc surface is not permanently altered when data is recorded

• Used to create and edit multimedia presentation

DIGITAL VERSATILE DISC

Known as digital video disc More data can be packed into the same amount of

space DVD disc can store 4.7 GB to 17 GB on a single DVD

disc-17 times the capacity of CDs Three basic type of DVDs: 1.Read only=DVD-ROM 2.Write once=DVD+R and DVD-R 3.Rewritable=DVD+RW,DVD-RW and DVD-RAM

Read only=DVD-ROM

• Known as DVD player

• Although it effective for distributing music they can only contain just over an hour of fair-quality video

• Can provide over two hours of high-quality video and sound

Write once=DVD+R and DVD-R

• Known as DVD recordable

• Used to create permanent archives for large amount of data and to record video

• Rapidly replacing CD-R drives due to their massive capacity

Rewritable=DVD+RW,DVD-RW and DVD-RAM

• Known as DVD random-access memory

• Able to read and use any of the formats

BLU-RAY DISC

Names comes from the blue-colored laser that is used to read the disc

Far greater capacity than DVDs

Capacity of 25 to 128 GB more than 20 times the capacity of a standard single-layer DVD

Blu-ray disc require special drivers

Most of this drivers are capable of reading standard DVDs and CDs in addition to Blu-ray.

SOLID-STATE STORAGE

Flash Memory

USB Drivers

Solid-State Drivers

Solid-state Drivers (SSDs)

• Faster and more durable than hard disks

• Require less power which can less to increased battery life for laptop and mobile devices

• More expensive and generally have a lower capacity than hard disks

• Widely used for tablet PCs such as iPad

Flash Memory• Widely used in

portable devices such as mobile phone and GPS navigation systems

• Used in variety of specialized input devices to capture and transfer data to desktop computers

• Used in digital media players like the iPod to store and play music and video files

USB Drives

• Connect directly to a computer’s USB port to transfer files and can have capacities ranging from 1 GB to 256 GB

• Have convenient size and large capacities

• Transporting data and information between computers

SECONDARY STORAGE

oCloud StorageoMass Storage Devices

oCareers in IT

• Internet acts as a “cloud” of servers that supply applications as a service rather than a product.

• These servers provide cloud storage also known as online storage.

• Eg:Google Docs-to create a word processing & spreadsheetsMint.com-for financial managementAmazon S3-storing data

• Cloud servers provide storage,processing, and memory• With cloud computing software installation and upgrade are avoided

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Cloud Storage

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MASS STORAGE DEVICE

• Mass storage refer to the tremendous amount of secondary storage required by large organization.

• Mass storage devices specialized high capacity secondary storage device designed to meet ognanizational demands of data

• Eg:floppy diskshard disksoptical disks

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ENTERPRISE STORAGE SYSTEM

To promote efficient and safe use of data across the networks within their organization5 mass storage devices:

File servers-dedicated computers with large storage capacities that provide users access to fast storage and retrieval of dataNetwork attached storage (NAS)-simpler and less expensive,widely used for home and small business storage need

RAID systems-larger versions of specialized devices-enhance organizational security by contantly making backup copies of files moving across the organization’s network Tape library-device automatic access to data achieved on a library tapeOrganizational cloud storage-high speed Internet connection to a dedicated remote organizational cloud storage server

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• An architecture to link remote computer storage device • Such as enterprise storage systems to computer available

as locally attached drives

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Storage Area Network (SAN)

Software Engineering• Analyze users’ needs and create

application software. Bachelor’s or advanced specialized accociate’s degree in computer science or information systems and extensive knowledge of computer and technology required. Salary range is $63 000 to $98 500.

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CAREERS IN IT