14c. Computer Systems Extra Storage

Memory Versus Storage

What is storage? The media on which data, instructions, and

information are kept, as well as the devices that record and retrieve these items

Memory Versus Storage

What is memory? A temporary

holding place for data and instructions

Consists of one or more chips on the motherboard

Sometimes called primary storage

Nonvolatile memory

Does not lose its contents when

power is removed from the computer

Volatile memory

Loses its contents when the computer’s power is turned off

Most memory is volatile

Floppy Disks

What is a floppy disk? A portable,

inexpensive storage medium

Consists of a thin, circular, flexible plastic disk with a magnetic coating

Enclosed in a square-shaped plastic shell

Today’s standard disk is 3.5” wide

Floppy Disks

What are the parts of a floppy disk? A thin circular

flexible film is enclosed between two liners

A piece of metal called a shutter covers an opening to the recording surface

shell

shutter

liner

magnetic coating

flexible thin film

metal hub

Floppy Disks

A device that can read from and write on a floppy disk

Most personal computers have a floppy disk drive, in which you insert and remove a floppy disk

What is a floppy disk drive (FDD)?

Floppy Disks

How does a floppy disk store data? A type of magnetic media Uses magnetic patterns to store

items such as data, instructions, and information on a disk’s surface

Able to access (read) data from and place (write) data on a magnetic disk any number of times

The read/write head in the floppy disk drive is the mechanism that actually reads items from or writes items on the floppy disk

Step 6: The read/write heads read data from and write data on the floppy disk.

Step 6

Step 5: A motor positions the read/write heads over the correct location on the recording surface of the disk.

Step 5

Step 4: A motor causes the floppy disk to spin.

Step 4

Step 3: If disk access is a write instruction, the circuit board verifies whether the disk can be written to or not.

Step 3

Step 2: When you initiate a disk access, the circuit board on the drive sends signals to control movement of the read/write heads and the disk.

Step 2

Step 1: When you insert the floppy disk into the drive, the shutter moves to the side to expose the recording surface on the disk.

Step 1

Floppy Disks

How does a floppy disk drive work?

Upward compatible

Able to recognize newer media

Floppy disk drives are not upward compatible

Floppy Disks

What is density? The number of bits

in an area on a storage medium

A floppy disk drive must support that floppy disk’s density

Most floppy disks today are high density (HD) with a capacity of 1.44 MB

Downward compatible

Able to recognize and use earlier media

Floppy disk drives are downward compatible

HiFD™ (High-Capacity

Floppy Disk) drive

Uses a 200 MB HiFD™ disk

Developed by Sony Electronics, Inc.

High-Capacity Disks

What is a high-capacity disk drive? A disk drive that uses disks with capacities of 100 MB

and greater

SuperDisk™ drive

Uses a 120 MB or a 250 MB SuperDisk™

Developed by Imation

Zip® drive

Uses a Zip® disk that can store 100 MB or 250 MB of

data

Developed by Iomega Corporation

built in Zip® drive

High-Capacity Disks

What is a backup? A duplicate of a file, program, or

disk that you can use if the original is lost damaged, or destroyed

High-capacity disks are often used to back up important data and information

Hard Disks

What a hard disk? Consists of several

inflexible, circular platters that store items electronically

Also called a hard disk drive or a fixed disk

A platter is coated with a material that allows items to be recorded magnetically on its surface

The components of a hard disk are enclosed in an airtight, sealed case to protect them

Step 4: The head actuator positions the read/write head arms over the correct location on the platters to read or write data

Step 4

Step 2: A small motor spins the platters while the computer is running

Step 2

Step 3: When software requests a disk access, the read/write heads determine the current or new location of the data

Step 3

Step 1: The circuit board controls the movement of the head activator and a small motor

Step 1

Hard Disks

How does a hard disk work?

Hard Disks

What is a cylinder? The location of a

single track through all platters

A single movement of the read/write head arms can read all the platters of data

trackcylinder

Hard Disks

What is a head crash? Occurs when a read/write head touches the surface of a

platter The platters of the hard disk rotate at a high rate of

speed while the computer is running The spinning creates a cushion of air that floats the

read/write head above the platter

Hard Disks

How does access time compare for a hard disk and a floppy disk?

A hard disk’s access time is significantly faster than a floppy disk• The hard disk spins

much faster than a floppy disk

• A hard disk spins constantly, while a floppy disk starts spinning only when it receives a read or write command

Hard disk

Approximately 5 to 11

milliseconds

Floppy disk

84 milliseconds or approximately ½ a

second

Hard Disks

What is a partition? You can divide a

formatted hard disk into separate areas called partitions

Done by issuing a special operating system command

Each partition functions as if it were a separate hard disk drive

drive C

Designation for first partition or for a single

partition on the hard disk

drive D

Designation for second partition on the hard

disk

Hard Disks

What is a removable hard disk? A disk drive in which a plastic or metal case surrounds

the hard disk so you can remove it from the drive A popular, reasonably priced, removable hard disk is the

Jaz® disk by Iomega

Hard Disks

What is an Internet hard drive? A service on the

Web that provides storage to computer users

Sometimes called online storage

Many offer storage free of charge

Revenues come from advertisers

Allows offsite backups of data

Others can be authorized to access

data from your Internet hard drive

Files can be accessed from any computer or device

that has Web access

Large audio, video, and graphics files can be downloaded to an

Internet hard drive instantaneously

Hard Disks

What are advantages of an Internet hard drive?

Compact Discs

What is a compact disc (CD)? A flat, round, portable,

metal storage medium that usually is 4.75 inches in diameter and less than one-twentieth of an inch thick

Most personal computers today include some type of compactdisc drive

Also called an optical disc

Available in a variety of formats

Step 3: Reflected light is deflected to a light-sensing diode, which sends digital signals of 1 to the computer. Absence of reflected light is read as a digital signal of 0.

Step 1: A laser diode shines a light beam toward the compact disc.

Step 2: If light strikes a pit, it scatters. If light strikes land, it is reflected back toward the laser diode.

Compact disc label

Compact disc label

lens lens

prism prism

laser diode

laser diode

Step 1Compact disc

label

lens lens

prism prism

laser diode

laser diode

Items are stored using microscopic pits (indentations) and land (flat areas) that are in the middle layer of the disk

A laser light reads items from the compact disc

Compact Discs

How does a laser read data on a compact disc?

Step 2Compact disc

label

lens lens

prism prism

laser diode

laser diode

pit land

Step 3Compact disc

label

lens lens

prism prism

laser diode

laser diode

Light-sensing

diode

Light-sensing

diode

0 1

pit land

CD-ROMs

What is a CD-ROM? A silver-colored compact disc

that uses the same laser technology as audio CDs for recording music

Can contain text, graphics, audio, and video

The manufacturer writes, or records, the contents of standard CD-ROMs

You cannot erase or modify the contents

A CD-ROM drive or CD-ROM player is used to read items on a CD-ROM

CD-ROMs

What is the storage capacity of a CD-ROM? A typical CD-ROM holds

about 650 MB of data, instructions, and information

Manufactures use CD-ROMs to store and distribute today’s multimedia and other complex software

CD-ROMs

What is a PhotoCD? A compact disc that contains digital photographic

images saved in the PhotoCD format Based on a file format developed by Eastman Kodak Used by commercial and

professional users A multisession disc, which

means you can write additional data, instructions, and information to the disc at a later time

CD-ROMs

A single-session disc offered by Kodak

Stores digital versions of photographs for consumers

Single-session means all items are written to the disc at one time

Film developers create the images on the disc from photographic negatives at the time a roll of film is developed

What is a Picture CD?

CD-R and CD-RW

What is a CD-R (compact disc-recordable)? A multisession compact disc onto which you can

record your own items such as text, graphics, and audio

You write on the CD-R using a CD recorder or a CD-R drive and special software

The CD-R drive can read and write both audio CDs and standard CD-ROMs

You cannot erase the disc’s contents

Most CD-ROM drives can read a CD-R

CD-R and CD-RW

What is a CD-RW (compact disc-rewritable)? An erasable disc you can write on multiple times You must have CD-RW software

and a CD-RW drive Discs can be read only by

multiread CD-ROM drives

• Drives that can read audio CDs, data CDs, CD-Rs, and CD-RWs

• Most recent CD-ROM drives are multiread

DVD-ROMs

What is a DVD-ROM (digital video disc-ROM)? An extremely high capacity

compact disc capable of storing from 4.7 GB to 17 GB

You must have a DVD-ROM drive or DVD player to read a DVD-ROM

Looks just like a CD-ROM but data, instructions, and information is stored in a slightly different manner to achieve a higher storage capacity

DVD-ROMs

How does a DVD-ROM store data? Three storage techniques used to store DVD-ROM data

• Pits are packed closer together to make the disc more dense

• Two layers of pits are used, where the lower layer is semitransparent so the laser can read through it to the upper layer

• Some are double-sided, which means you can remove the DVD-ROM and turn it over to read the other side

Tapes

What is tape? A magnetically coated ribbon of plastic capable of storing large

amounts of data and information at a low cost A tape drive reads from and writes data and information on a tape Older computers used reel-to-reel tape drives A tape cartridge is a small, rectangular, plastic housing for tape

used in today’s tape drives

Tapes

Where is tape used? Used by business and home users to backup personal

computer hard disks Both external and internal tape units for personal

computers Larger computers use tape cartridges mounted in a

separate cabinet called a tape library Three common types of tape drives

Tapes

What is sequential access versus direct access?

Sequential access

Method used for tape

Reading and writing data consecutively

You must forward or rewind the tape to a specific point to access

a specific piece of data

Much slower

Utilized most often for long-term storage and backup

Direct access

Method used for floppy disks, hard disks, and compact discs

Also called random access

You can locate a particular data item or file immediately, without having to move consecutively

through items stored in front of the desired data item or file

Faster

Used as the primary method of storage

NAS device Internet backupNAS deviceNAS device

CD-ROM jukeboxes

Internet backup

tape library

NAS device

CD-ROM jukeboxes

Internet backup

RAID

SAN

servers

tape library

NAS device

CD-ROM jukeboxes

Internet backup

Enterprise Storage Systems

What is an enterprise storage system? A strategy that

focuses on the availability, protection , organization, and backup of storage in a company

Goal is to consolidate storage so operations run as efficiently as possible

Network-attached storage (NAS) device

An easy way to add additional hard disk space to the network

Internet backup

Stores data, information, and instructions on the

Web

CD-ROM jukebox

Holds hundreds of CD-ROMs that can contain application

programs and data

Also called a CD-ROM server

RAID system

Ensures that data is not lost if one drive fails

Server

Stores data, information, and instructions need by

users on the networkTape library

A high-capacity tape system that works with multiple tape

cartridges for storing backups of data, information,

and instructions

Enterprise Storage Systems

What storage techniques are used in an enterprise system?

Storage area network (SAN)

A high-speed network that connects storage devices

Enterprise Storage Systems

How do organizations handle storage?

Enterprise storage system managed in

house

Data warehouse

A huge database system that stores and manages

historical and current transaction data

Storage management offloaded to an outside organization or online

Web service

PC Cards

What is a PC Card? A thin, credit card-sized device Fits into a PC Card slot on a notebook other personal

computer Different types and sizes add storage, additional

memory, communications, and sound capabilities to a computer

PC Cards

What are the uses of PC Cards?

Three types of PC Card Advantage of a PC Card for storage is portability

between systems

Miniature Mobile Storage Media

What is miniature mobile storage media? Handheld

devices use miniature mobile storage media to augment internal storage

Storage CapacityDevice Name Type, Use

Clik! Disk

CompactFlash

Microdrive

SmartMedia

40 MB

2 to 256 MB

1 GB

2 to 128 MB

Cartridge

Digital cameras, notebook computers

Memory Card

Digital cameras, handheld computers, notebook computers, printers, cellular telephones

Memory card

Digital cameras, handheld computers, music players, video cameras

Memory Card

Digital cameras, handheld computers, photo printers, cellular telephones

Miniature Mobile Storage Media

How is miniature storage media used?

Handheld devices, such as players and wallets, read or display the contents of miniature storage media such as memory cards

Miniature Mobile Storage Media

What is a smart card? Stores data on a thin

microprocessor embedded in the card

Similar in size to a credit card

Read smart card with a specialized card reader

Information on the smart card can be read and updated

Store data such as photographs, music, books,

and video clips

Miniature Mobile Storage Media

What are the types of smart cards? Intelligent smart

card contains a processor and has input, process, output, and storage capabilities

Memory card has only storage capabilities

Store a prepaid dollar amount that is updated when the card is

used

Store patient records, vaccination data, and other

healthcare information

Store tracking information such as customer purchases or

employee attendance

Miniature Mobile Storage Media

What is electronic money? A means of

paying for goods and services over the Internet

Also called digital cash

A bank issues unique digital cash numbers

that represent an amount of money

When you purchase digital

cash, the amount of money is

withdrawn from your bank account

To use the card you swipe it

through a card reader

Microfilm and Microfiche

What are microfilm and microfiche? Store microscopic images of

documents on roll or sheet film Images recorded onto film using

a computer output microfilm (COM) recorder

Images can only be read with a microfilm or microfiche reader

Microfiche

Uses a small sheet of film, usually

about four inches by six inches

Microfilm

Uses a 100- to 215-foot roll of film

Microfilm and Microfiche

How do life expectancies of various media compare?

Microfilm and microfiche are inexpensive and have the longest life of any storage medium