Chapter 7 - 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

What is memory?

° A temporary holding place for data and instructions

° Consists of one or more chips on the motherboard

° Sometimes called primary storage

How does storage differ from memory?

° Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage

° Storage holds items such as data, instructions, and information for future use

° Storage is nonvolatile

How does volatility compare?

What is a storage medium and a storage device?

What is reading and writing?

Reading

Process of transferring data, instructions, and information from a storage medium into memory

Serves as a source of input

What is access time?

° The amount of time it takes the device to locate an item on a disk

° Defines the speed of a disk storage device

What is capacity?

° The number of bytes (characters) a storage medium can hold

° Manufacturers use many terms to define the capacity of storage media

Technology Trailblazer

Al Shugart

° Joined IBM as a customer engineer in 1951

° Supervised a team in 1967 responsible for developing a removable, portable data storage device

° Founded Shugart Associates in 1973 and Seagate Technology in 1979

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

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

What is a floppy disk drive (FDD)?

° 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

How are floppy disk drives designated?

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

How does a floppy disk drive work?

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

What are tracks and sectors?

° Track: a narrow recording band that forms a full circle on the surface of the disk

° Pie shaped sections break the tracks into small arcs called sectors

° A sector can store up to 512 bytes of data

° A typical floppy disk stores data on both sides of the disk

What is a cluster?

° The smallest unit of disk space that stores data

° Also called an allocation unit

° 2 to 8 sectors depending on the operating system

° Each cluster holds data from only one file

° One file can span many clusters

What is formatting?

° The process of preparing a disk for reading and writing

° Formatting marks bad sectors as unusable

How do you care for a floppy?

° A floppy disk can last at least seven years

° Proper care helps to maximize a disk’s life

What is a write-protect notch?

° A small opening with a cover that you slide up or down

° Protects floppy disks from accidentally being erased

High-Capacity Disks

What is a high-capacity disk drive?

° A disk drive that uses disks with capacities of 100 MB and greater

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

How does a hard disk work?

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

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

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

What is a disk cache?

° A portion of memory that the processor uses to store frequently accessed items

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

What is a disk controller?

° A special purpose chip and associated electronic circuits that control the transfer of data, instructions, and information from a disk to the rest of the computer

° Sometimes called an interface

° A hard disk controller (HDC) is the interface for a hard disk

° May be part of the disk drive or a separate card inside the system unit

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

Company on the Cutting Edge

Kingston Technology

° The world’s leading independent manufacturer of memory
products of computers,
servers, digital cameras, and
other electronic devices

° Founded by John Tu and
David Sun in 1987

° Markets more than 2,000
products

° Designated as one of the 100 Best Companies to Work for in the United States by Fortune magazine

Hard Disks

What is RAID?

° Redundant array of independent disks

° A type of hard disk system that connects several smaller disks into a single unit that acts like a single large hard disk

° More reliable than a traditional disk system but quite expensive

How does RAID work?

° RAID duplicates data, instructions, and information to improve data reliability

What utilities
maintain a hard
disk drive?

° Windows provides many maintenance and monitoring utilities for a hard disk on the System Tools submenu

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

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 compact
disc drive

° Also called an
optical disc

° Available in a
variety of formats

How do you use a compact disc?

° CD drives can read compact discs, including audio discs

° Most CD drives include a volume control button and a headphone jack

° The drive designation of a CD drive usually follows alphabetically after that of the hard disk

How does a laser read data on a compact disc?

° 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

How is data stored on a compact disc?

° A compact disc typically stores items in a single track

° It spirals from the center of the disc to the edge of the disc

° The track is divided into evenly sized sectors in which items are stored

What is a jewel box?

° A protective case for a compact disc

° Place a compact disc in a jewel box to protect data

How should you care for a compact disc?

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

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

What is the data transfer rate of a CD-ROM drive?

° The time it takes a drive to transmit data, instructions, and information from the drive to another device

° Slower CD-ROM drives produce choppy images or sound

° Drive speed measured relative to original CD-ROM drives (150 KB per second)

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

What is a Picture CD?

° 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

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

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

How is an audio
CD created?

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

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

What are other various DVD formats?

Technology Trailblazer

Mark Dean

° Designs microprocessors, improvements in architecture, and hardware innovations for IBM

° First African-American to receive an IBM Fellowship, the company’s highest technical ranking

° Inducted into the National Inventor's Hall of Fame

Company on the Cutting Edge

EMC2

° A provider pf storage systems for some of the world’s largest corporations

° Founded in 1979 by Richard Egan and Roger Marino to fill a demand for add-on memory boards in the minicomputer market

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

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

What is sequential access versus direct access?

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

What storage techniques are used in an enterprise system?

How do organizations handle storage?

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

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

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

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

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

What is electronic money?

° A means of paying for goods and services over the Internet

° Also called digital cash

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

How do life expectancies of various media compare?

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

Summary

What are suggested storage devices for computer users?

Summary of Storage

° Memory versus storage

° Floppy disks

° High-capacity disks

° Hard disks

° Compact discs

° CD-ROMs

° CD-R and CD-RW

° DVD-ROMs

° Tapes

° Enterprise storage systems

° PC Cards

° Miniature mobile storage media

° Microfilm and microfiche

Chapter 7 Complete