csc1100 - chapter05 - storage

Discovering Computers 2008

Chapter 5 Chapter 5 Chapter 5 Chapter 5

StorageStorageStorageStorage

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Chapter 5 ObjectivesChapter 5 ObjectivesChapter 5 ObjectivesChapter 5 Objectives

Differentiate between storage devicesand storage media

Differentiate between storage devicesand storage media

Describe the characteristics ofmagnetic disks

Describe the characteristics ofmagnetic disks

Describe the characteristics of Describe the characteristics of

Differentiate among CD-ROMs,recordable CDs, rewritable CDs,

DVD-ROMs, BD-ROMs, HD DVD-ROMs, recordable DVDs, and

rewritable DVDs

Differentiate among CD-ROMs,recordable CDs, rewritable CDs,

DVD-ROMs, BD-ROMs, HD DVD-ROMs, recordable DVDs, and

rewritable DVDs

Identify the uses of tapeIdentify the uses of tapeDescribe the characteristics of a hard disk

Describe the characteristics of a hard disk

Discuss various types of miniature, external, and removable hard disksDiscuss various types of miniature, external, and removable hard disks

Describe the characteristics of optical discs

Describe the characteristics of optical discs

Identify the uses of tapeIdentify the uses of tape

Discuss PC Cards, ExpressCard modules, and the various types of

miniature storage media

Discuss PC Cards, ExpressCard modules, and the various types of

miniature storage media

Identify uses of microfilm and microfiche

Identify uses of microfilm and microfiche

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Learning OutcomeLearning OutcomeLearning OutcomeLearning Outcome

Successful students will be able to:

Describe the characteristics of computer hardware devices and explain their functionalities.

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What is storage?� Holds data, instructions, and information for future use� Storage mediumis physical material used for storage

� Also called secondary storage

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What is capacity?

Kilobyte (KB) 1 thousand

Megabyte (MB) 1 million

Gigabyte (GB) 1 billion

� Number of bytes (characters) a storage medium can hold

Gigabyte (GB) 1 billion

Terabyte (TB) 1 trillion

Petabyte (PB) 1 quadrillion

Exabyte (EB) 1 quintillion

Zettabyte (ZB) 1 sextillion

Yottabyte (YB) 1 septillion

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How does volatility compare?� Storage medium is nonvolatile—contents retained when

power is off

ON OFF

� Memory is volatile—holds data and instructions temporarily

Storage Medium(floppy disks, Zip disks,

hard disks, CDs)No

nvo

lati

le

Contents Contents retainedretained

Contents Contents available to useravailable to user

Memory(most RAM)

(chips on motherboard)

Screen Display

Vola

tile Display Display

disappearsdisappears

Data andData andinstructions instructions

available to useravailable to user

Display Display appearsappears

Data and Data and instructions erasedinstructions erased

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WritingWritingProcess of transferring Process of transferring

WritingWritingProcess of transferring Process of transferring


What is a storage device?

ReadingReadingProcess of transferring Process of transferring

ReadingReadingProcess of transferring Process of transferring

Hardware that Hardware that records and records and

retrieves items retrieves items Process of transferring Process of transferring items from memory items from memory

to storage mediato storage media

Process of transferring Process of transferring items from memory items from memory

to storage mediato storage media

Process of transferring Process of transferring items from storage items from storage media to memorymedia to memory

Process of transferring Process of transferring items from storage items from storage media to memorymedia to memory

to and from to and from storage mediastorage media

Functions as source of input

Creates output

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Primary Storage

Items waiting to be interpretedand executedby the processor

Memory (most RAM)

Stores …Transfer rates


What is access time?� Time it takes storage device to locate item on storage medium� Time required to deliver item from memory to processor

fastertransfer

rates

Floppy Disk Small filesto be transported

Secondary Storage

Hard Disk

Flash Memory Cards and USB Flash Drives

CDs and DVDs

Tape

and executedby the processor

Operating system, applicationsoftware, user data and informationDigital pictures or filesto be transported

Software, backups, movies, music

Backupsslowertransfer

rates

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Access time & Transfer rateAccess time & Transfer rateAccess time & Transfer rateAccess time & Transfer rate

Memory accesses items in billionths of a second (nanoseconds)

Storage devicesaccess items in:� thousandths of a second (milliseconds) or

millionths of a second (microseconds)� millionths of a second (microseconds)

Transfer rate is the speed with which data, instruction & info transfer to & from a device, stated as:� KBps & MBps

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Magnetic DisksMagnetic DisksMagnetic DisksMagnetic Disks

� Use magnetic particles to store items on a disk’s surface

� Alignment of magnetic particles represents the data – either a 0 bit or a 1 bit

� Must be formatted first:Must be formatted first:� Dividing the disk into tracks & sectors, so the OS can

store & locate items on disk

� A sector stores up to 512 bytes of data

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Trackis narrow

recording bandthat forms fullcircle on disk

Sectorstores up to512 bytesof data

Formatting prepares disk for use

circle on disk of data

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� For reading & writing purpose, sectors (2-8, depending on OS) are grouped into clusters

� Cluster (allocation unit) is the smallest unit of disk space that stores an item

� Each cluster holds data from only one fileEach cluster holds data from only one file� Even if a file consists of only few bytes, it uses an

entire cluster� One file, anyhow, can span many clusters

� Sometimes, a sector has defect & cannot store data. When format, OS marks these bad sectors as unusable

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What is ahard disk/hard disk drive/hard drive ?hard disk mounted

in system unit

� High-capacity storage: 80 – 750GB & more

� Consists of several inflexible, circular platters that store items electronically

� Components enclosed in airtight,

Perpendicular recording

� Components enclosed in airtight, sealed casefor protection

Longitudinal recording

Fixed h/d & portable h/d

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What are characteristics of a hard disk?

Sample Hard Disk Characteristics

Advertised capacity 500 GB

Platters 4

Read/write heads 8

Cylinders 16,383Cylinders 16,383

Bytes per second 512

Sectors per track 63

Sectors per drive 973,773,168

Revolutions per minute 7,200

Transfer rate 300 MB per second

Access time 8.5 ms

actualdisk

capacity

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� h/d capacity determined from num of plattersand composition of magnetic coatingon the platters

� Platter� diameter: 3.5 inches in– desktop; 2.5 inches – notebook &

mobile devices� made of aluminum, glass or ceramic– coated with alloy–� made of aluminum, glass or ceramic– coated with alloy–

allow items to be recorded magnetically on its surface. The coating is 3 millionths of an inchthick

� Each has 2 read/write heads, one for each side

� h/d armsmove read/write heads to the proper location –read & write items in the drive as it barely touches the disk/s recording surface

� Location of read/write heads referred to by its cylinder– a vertical section of a track that passes through all platters

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How does a hard disk work?

Step 2.Small motor spins

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

Step 1.Circuit board controls movement of head actuator and a small motor.

Small motor spins platters while computer is running.

Step 4.Head actuator positions read/write head arms over correct location on platters to read or write data.

platters rotate at high speed: 5400 – 15000 revolutions per minute (rpm)– until power is removed

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What is acylinder?� Vertical section of

track through all platters

� Single movement of read/write head arms accesses all

plattertrack

sector

arms accesses all plattersin cylinder read/write

head

platter

sides

cylinder

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What is ahead crash?

� Spinning creates cushion of air that floats read/write head above platter� Occurs when read/write head touches platter surface

� A smoke particle, dust particle, or human hair could render drive unusable� Clearance between head and platter is approximately two-millionths of an inch

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What is a disk cache/buffer?� Portion of memory

(memory chip on h/d) that processor uses to store frequently accessed items

� 2MB – 16MB (the greater, the faster the (the greater, the faster the h/d)

secondrequestfor data—to hard disk

first requestfor data—to disk cache

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What is RAID ?� Redundant Array of Independent Disks� Connects multiple smaller disks into a single unit that

acts as a single large hard disk

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

separate storage medium that user can use in case the original is lost, damaged or destroyed

What is density?� Number of bits in an area on a storage medium� High density = high capacity

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Backup methodBackup methodBackup methodBackup method---- Hard DisksHard DisksHard DisksHard Disks

How does RAID work?Disk system that duplicates data, instructions, and information to improve data reliability

� Mirroring has one backup disk for each disk� Striping stores data across multiple disks

mirroring(RAID Level 1)

striping

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What is a miniature hard disk?� Provide greater storage capacities than flash memory:

4GB – 160GB– mostly use perpendicular recording� Smaller than notebook computer hard disks� A pocket hard drive is a self-contained unit

� User can insert in & remove from a slot in a device or � User can insert in & remove from a slot in a device or a computer or plug-in a USB port on a computer

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What are external hard disksand removable hard disks?

External hard disk—freestandinghard disk that connects to system unit

Removable hard disk—hard diskthat you insert and removefrom hard disk drive

� Used to back up or transfer files

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External & Removable Hard DiskExternal & Removable Hard DiskExternal & Removable Hard DiskExternal & Removable Hard Disk

External h/d:�Connects with cable to USB or FireWire port on SU�Some include multiple h/d act as one, having capacity up to 1TB

Removable h/d:�Sometimes the drive is built in the SU�Sometimes the drive is built in the SU�Others are external devices – connect with cable to USB or

FireWire port on SU.�Has up to 500GB capacity

ADVANTAGES??

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SATASATA (Serial Advanced Serial Advanced Technology AttachmentTechnology Attachment) controller ) controller uses serial signals to transfer data, uses serial signals to transfer data,


What is a disk controller?

Chip and circuits Chip and circuits that control transfer that control transfer of items from diskof items from disk

SCSISCSIcontroller supports up to fifteencontroller supports up to fifteendevices including hard disks, CDdevices including hard disks, CD

and DVD drives, tape drives, printers,and DVD drives, tape drives, printers,scanners, network cardsscanners, network cards

uses serial signals to transfer data, uses serial signals to transfer data, instructions, and informationinstructions, and information

EIDEEIDE (EEnhancednhancedII ntegratedntegratedDDrive rive EElectronics) controller supports four lectronics) controller supports four hard disks, provides connections for hard disks, provides connections for

CD and DVD drivesCD and DVD drives

of items from diskof items from disk

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What is online storage?� Service on Webthat provides storage for

minimal monthly fee� Files can be accessed from

any computer with Web access

� Large files can be downloaded

� Others can be authorized to access your data

Large files can be downloaded instantaneously

REASONS??

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What is a floppy disk?� Portable, inexpensive storage medium

(also called diskette)� Consists of thin, circular, flexible plastic

Mylar film with magnetic coating� Enclosed in 3.5” wide plastic shell

Storage capacity: 1.44MB� Storage capacity: 1.44MB� Access time: 84 ms� Transfer rate: 250 – 500KBps� Contains 80 track on each side� ≈ 18 sectors per track

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shutter

liner

metal

shellmagnetic coating

flexible thin film

metal hub

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sector18 per track

track80 per

side


80 tracks per side X 18 sectors per track X 2 sides per disk X 512 bytes per sector = 1,474,560 bytes

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Optical DiscsOptical DiscsOptical DiscsOptical Discs

What are optical discs?� Flat, round, portable

metal discs made of metal, plastic, and lacquer

� Can be read only or Insert the disc,

Push the button toslide out the tray.

Push the same buttonto close the tray.

� Most PCs include an optical disc drive

� Can be read only or read/write

Insert the disc,label side up.

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How does a laser read data on an optical disc?

disc label

laserdiode

laserdiode

prism prism

light-sensingdiode

light-sensingdiode

0 1

lens lenspit land

Step 1.Laser diode shines a light beam towarddisc.

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

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

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How is data stored on an optical disc?� Typically stored in

single track� Track divided

into evenly sizedsectorssizedsectorsthat store items

single trackspirals to edgeof disc

disc sectors

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How should you care for an optical disc?

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What is a CD-ROM?� Compactdisc read-only memory� Single-session disc� Cannot erase or modify contents� Typically holds 650 MB to 1 GB� Commonly used to distribute multimedia and complex software

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

75XRanges from 48X to 75X

or fasteror faster

75 75 ×××××××× 150 KBps = 11,250 KBps 150 KBps = 11,250 KBps or 11.25 MBpsor 11.25 MBpsX is 150 KBps X is 150 KBps

(KB per second)(KB per second)

48X: 48X: 48 48 ×××××××× 150 KBps = 7,200 KBps 150 KBps = 7,200 KBps

or 7.2 MBpsor 7.2 MBps

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What is a Picture CD?

Film developers offer

Picture CD service

Can be modified

using photo editing software

Stores digital versions of roll of film service editing software

Step 3.At home, print images from Picture CD on your ink-jet photo printer.

At a store, print images to Picture CD at kiosk.

Step 1.Drop off film to be developed. Mark the Picture CD box on the film-processing envelope.

Step 2.When you pick up prints and negatives, a Picture CD contains digital images of each photograph.

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What are CD-Rs and CD-RWs? Must haveCD recorder

or CD-R drive

Cannot erasedisc’s contents

CD-R (compact disc-recordable)— multisession optical disc— can write on once, but not erase

CD-RW (compact disc-rewritable)—ceerasable multisession disc— can write on multiple times

Must haveCD-RW softwareand CD-RW drive

Disc reliabilitydrop with each successive rewriteSpeed: 52/24/52 [write – 52X or more, rewrite –24X or more, read – 52X or more ]

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CDCDCDCD----R and CDR and CDR and CDR and CD----RW drivesRW drivesRW drivesRW drives

CD-R drive

(speed: 40/48)

writes

CD-RW drive

(speed: 52/24/52)

+ CD-RW software

writes

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CDCDCDCD----R and CDR and CDR and CDR and CD----RW drivesRW drivesRW drivesRW drives

CD-R drive

(speed: 40/48)

reads

CD-RW drive

(speed: 52/24/52)

reads

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Video CDVideo CDVideo CDVideo CD

� Store video on a CD-R

� Can be played in CD or DVD drives, DVD players & some game consoles

� Hold 74 – 80 minutes of Hold 74 – 80 minutes of video

copy Digital media

RIPPING

PROCESS

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What is aDVD-ROM (digital versatile disc-ROM or digital video disc-ROM)?� Must haveDVD-ROM drive or

DVD player to read DVD-ROM� Stores databases, music,

complex software, and moviescomplex software, and movies� Blu-ray discshave storage

capacity of up to 100 GB� HD-DVD discshave storage

capacity of up to 60 GB� UMD can store up to 1.8 GB

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How does a DVD-ROM store data?1. Dense disc – closer pits2. Two layers of pits are used, lower layer is

semitransparent so laser can read through3. Some are double-sided

Many types of recordable and rewritable DVDs are available� DVD-R and DVD+R� DVD-RW and DVD+RW

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TapeTapeTapeTape

What is tape?� Magnetically coated plastic ribbon

capable of storing large amountsof data at low cost

� Primarily used for backup� Low cost� Long term storage

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TapeTapeTapeTape

How is data stored on a tape?� Sequential access

� Unlike Direct access/Random access— used on hard disks, CDs, and DVDs — which can

� Reads and writes data consecutively, like music tape

on hard disks, CDs, and DVDs — which can locate particular item immediately

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PC Cards and ExpressCard ModulesPC Cards and ExpressCard ModulesPC Cards and ExpressCard ModulesPC Cards and ExpressCard Modules

What are PC Cards and ExpressCard Modules?� Adds capabilities to computer

� Credit-card-sized device commonly used in notebook computers

� Add memory, storage, communications, multimedia, and security capabilities to a computermultimedia, and security capabilities to a computer

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Miniature Mobile Storage MediaMiniature Mobile Storage MediaMiniature Mobile Storage MediaMiniature Mobile Storage Media

What is miniature mobile storage media?� Storage for small mobile devices

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What are common types of flash memory cards?

CompactFlash Secure Digital xD Picture Card

Memory Stick Memory Stick PRO Duo

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How does one type of flash memory card work?

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What is a USB Flash Drive?� Plugs in a USB port on a

computer or mobile device� Storage capacities up to 64 GB� May eventually make the

floppy disk obsolete� Also called U3 Smart device� Also called U3 Smart device� Transfer rate: 12 MBps

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What is a smart card?� Stores data on microprocessor embedded in small card� Input, process, output, and storage capabilities� Used to store medical records, vaccination data, and other

health-case and identification information; tracking information – employee attendance or customer purchase, authenticating users for building accessusers for building access

Are credit cards smart cards?

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Microfilm and MicroficheMicrofilm and MicroficheMicrofilm and MicroficheMicrofilm and Microfiche

What are microfilm and microfiche?

Images recorded using Images recorded using computer output microfilm recordercomputer output microfilm recorder

Store microscopic images of Store microscopic images of documents on roll or sheet of filmdocuments on roll or sheet of film

computer output microfilm recordercomputer output microfilm recorder

Microfilm — 100- to215-foot roll of film

Microfiche — small sheet of film, usually 4” ×××× 6”

� Used to store back issues of newspapers, magazines, inactive files, transactions and cancelled checks,…

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Microfilm and MicroficheMicrofilm and MicroficheMicrofilm and MicroficheMicrofilm and Microfiche

How do life expectancies of various media compare?� Microfilm and microfiche are inexpensive % have longest life of

any storage media

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Putting It All TogetherPutting It All TogetherPutting It All TogetherPutting It All Together

What are recommended storage devices for home users?

� 250 GB hard disk� Online storage� CD or DVD drive� Card reader/writer� Card reader/writer� USB flash drive

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What are recommended storage devices for small office/home office (SOHO) users?

� 500 GB hard disk� Online storage� CD or DVD drive� External hard drive for backup� External hard drive for backup� USB flash drive

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What are recommended storage devices for mobile users?

� 100 GB hard disk� Online storage� CD or DVD drive� Card reader/writer� Card reader/writer� Portable hard disk for backup� USB flash drive

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What are recommended storage devices for power users?

� 1.5 TB hard disk� Online storage� CD or DVD drive� Portable hard disk for backup� Portable hard disk for backup� USB flash drive

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What are recommended storage devices for large business users?

� Desktop computer�500 GB hard disk�CD or DVD drive�Smart card reader�Smart card reader�Tape drive�USB flash drive

� Server or Mainframe�Network storage server�40 TB hard disk system�CD-ROM or DVD-ROM server�Microfilm or microfiche

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Summary of StorageSummary of StorageSummary of StorageSummary of Storage

Internal hard disksInternal hard disks

External and removable hard disksExternal and removable hard disks

Floppy disksFloppy disks

HD DVD discsHD DVD discs

Recordable and Rewritable DVDsRecordable and Rewritable DVDs

TapeTapeCD-ROMsCD-ROMs

Recordable and Rewritable CDsRecordable and Rewritable CDs

DVD-ROMsDVD-ROMs

Blu-ray Discs (BDs)Blu-ray Discs (BDs)

TapeTape

PC Cards and ExpressCard modules

PC Cards and ExpressCard modules

Flash memory cards and USB flash drives

Flash memory cards and USB flash drives

Chapter 5 Complete

Smart cards, microfilm, and microfiche

Smart cards, microfilm, and microfiche

csc1100 - chapter05 - storage

Technology

magnetic disks hard

storage medium time

bytes of data

storage devicesrecordable

highcapacity storage

storage mediadvdroms

future use storage medium

hard disk work