Ch5 storagedevices(updated)

Chapter 5Chapter 5

Types of Storage Devices

Describing Storage Describing Storage DevicesDevicesStorage devices hold data

permanently, even when the computer is turned off.

Two processes◦Writing data◦Reading data

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Describing Storage Describing Storage DevicesDevices Storage terms

The physical material that actually holds data is called a storage medium.

A floppy disk is a storage medium.

The hardware that writes data to or reads data from a storage medium is called a storage device.

A floppy disk drive is a storage device.

• Types of Storage Devices:1.Magnetic devices use a magnet2.Optical devices use lasers3.Solid-state devices have physical switches

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1.1. Magnetic Storage Magnetic Storage DevicesDevices

The primary types of magnetic storage are:1. Hard disks.2. floppy disks(Diskettes).3. High-capacity floppy disks.4. magnetic tape.

All magnetic drives work the same

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Floppy DiskFloppy Disk Hard DiskHard Disk

TapeTape

Magnetic Storage DevicesMagnetic Storage DevicesData storage and retrieval

◦ A magnetic disk's medium contains iron particles,

◦ A disk drive uses read/write heads containing

electromagnets to create magnetic charges on the

medium.

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Magnetic Storage DevicesMagnetic Storage DevicesData organization

◦ Disks must be formatted before useDetermines how data will be stored:

◦ Format draws tracks on the disk◦ Tracks is divided into sectors

Purpose of formatting a magnetic disk:Before the computer can use a magnetic disk

to store data, the disk’s surface must be magnetically formatted, so that the computer can go directly to a specific point on it without searching through data.

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Tracks and SectorsTracks and Sectors

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Magnetic Storage DevicesMagnetic Storage DevicesFinding data on diskEach track and sector is labeled◦ Listing of where files are stored

File Allocation Table (FAT) – a log that records each File's location

and each sector's status FAT32 NTFS

◦ The OS(Operating system) organizes sectors into groups, called clusters

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Magnetic Storage DevicesMagnetic Storage Devices

1. Diskettes◦ Also known as floppy disks◦ Spin at 300 RPM◦ Takes .2 second to find data◦ 3 ½ floppy disk holds 1.44 MB

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2. Hard disks◦ Primary storage device in a

computer◦ 2 or more aluminum platters◦ Each platter has 2 sides◦ Spin between 5,400 to 15,000 RPM◦ Data found in 9.5 ms or less◦ Drive capacity greater than 40 GB

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Illustrated Hard DiskIllustrated Hard Disk

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Contain multiple disks called Contain multiple disks called plattersplatters


3. Removable high capacity disks◦Speed of hard disk◦Portability of floppy disk◦There are 2 types :

1. High capacity floppy disk• Stores up to 750 MB of data

2. Hot swappable hard disks• Provide GB of data• Connect via USB

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Hot swappable hard disks

•Hot swappable hard disk : can be removed and replaced while the computer is still running.


4. Tape drives◦ Best used for

Infrequently accessed data Back-up solutions

◦ Slow sequential access◦ Capacity exceeds 200 GB

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Optical Storage DevicesOptical Storage Devices List seven types of optical storage

devices commonly used in PCs.1. Compact Disc Read-Only Memory (CD-ROM).2. CD-Recordable (CD-R).3. CD-ReWritable (CD-RW).4. Digital Video Disc Read-Only Memory (DVD-

ROM).5. DVD-Recordable (DVD-R).6. DVD-ReWritable (DVD-RW).7. PhotoCD.

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Optical Storage DevicesOptical Storage DevicesCD-ROM

◦Most software ships on a CD◦Read using a laser◦Written from the inside out◦Standard CD holds 650 MB

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Recordable Optical Recordable Optical TechnologiesTechnologiesCD Recordable (CD-R)

◦Create a data or audio CD◦Data cannot be changed◦Can continue adding until full

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Recordable Optical Recordable Optical TechnologiesTechnologiesCD Rewritable (CD-RW)

◦Create a reusable CD◦Can reuse about 100 times

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Recordable Optical Recordable Optical TechnologiesTechnologiesPhoto CD

◦Provides for photo storage◦Photos added to CD until full◦Original pictures cannot be changed

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Optical Storage DevicesOptical Storage DevicesDVD-ROM

◦Digital Video Disk◦Use both sides of the disk◦Capacities can reach 18 GB◦DVD players can read CDs

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Recordable Optical Recordable Optical TechnologiesTechnologiesDVD Recordable (DVD-R)

◦Allows home users to create DVDs◦Data cannot be changed

DVD-RAM◦Allow reusing of DVD media

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Solid State DevicesSolid State DevicesData is stored physically

Store data on memory circuits.

No magnets or laserVery fastThe primary types of Solid State

Devices are:1. Flash memory 2.Smart cards 3.Solid-state disks

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Solid State DevicesSolid State DevicesFlash memory

◦Found in cameras and USB drives◦Combination of RAM and ROM◦Long term updateable storage

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Solid State DevicesSolid State DevicesSolid-state disks

◦Large amount of SDRAM◦Extremely fast.◦Require battery backups◦Most have hard disks copying data

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Solid State DevicesSolid State DevicesSolid-state disks

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Solid State DevicesSolid State DevicesSmart cards

◦Credit cards with a chip◦Chip stores data◦A smart card contain memory and

microprocessor components. ◦The card is made of plastic.◦Hotels use for electronic keys

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QuestionsQuestions1. List four types of magnetic storage

devices commonly used in PCs.2. List seven types of optical storage

devices commonly used in PCs.3. Name three types of solid-state

storage devices.4. What is the purpose of formatting a

magnetic disk?5. What is the storage capacity of a

standard floppy disk?

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Measuring and Improving Drive Performance

Drive PerformanceDrive PerformanceAverage access time

◦Also known as seek time◦Time to find desired data◦Measured in milliseconds(ms)◦Hard drive between 6 and 12 ms◦CD between 80 and 800 ms

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Drive PerformanceDrive PerformanceData transfer rate

◦the amount of data that one device can send to another in a given amount of time.

◦Measured in Bps(megabytes per second )

◦Hard drive ranges from 15 to 160 MBps

◦Floppy disks transfer at 45 KBps

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Data Transfer RateData Transfer Rate

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Optimizing PerformanceOptimizing Performance

1. Disk optimization◦Handled by operating system(OS)

tool◦Routine disk maintenance◦Optimization should be run monthly

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2. Clean up unnecessary files◦Delete temp files◦Uninstall unused programs◦Delete obsolete data files◦Files should be cleaned weekly

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3. Scan a disk for errors◦Bad spots on the media◦Find and fix the error

Move data to a good spot Mark the spot as bad

◦Disks should be scanned monthly

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4. Defragment a disk◦Files fragment when resaved◦Fragmented files load slower◦Defragment puts the fragments

together◦Disks should be defragged monthly

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DefragmentDefragment

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5.File compression◦Shrinks the size of a file◦Takes up less space on disk◦Reduce a disks performance◦Will increase disk capacity◦PKZip, WinZip and WinRAR

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File CompressionFile Compression

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763 KB763 KBon diskon disk

CompressedCompressed157 KB157 KB

Chapter 6Chapter 6End of Chapter

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Ch5 storagedevices(updated)