Intro_Ch_06A_Br

7/28/2019 Intro_Ch_06A_Br

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Copyright 2006 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill Technology Education

McGraw-Hill Technology Education Copyright 2006 by The McGraw-Hill Companies, Inc. All rights reserved.


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Chapter 6A & B

Types of StorageDevices &

Measuring andImproving Drive

Performance


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6A-3

Describing Storage Devices

Store data when computer is off Two processes

Writing data

Reading data


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6A-4

Describing Storage Devices

Storage terms Media is the material storing data

Storage devices manage the media

Magnetic devices use a magnet

Optical devices use lasers

Solid-state devices have physical switches


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6A-5

Magnetic Storage Devices

Most common form of storage Hard drives, floppy drives, tape

All magnetic drives work the same


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6A-6


Floppy Disk

Hard Disk

Tape


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Data organization Disks must be formatted before use

Format draws tracks on the disk

Tracks is divided into sectors Amount of data a drive can read


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Tracks and Sectors


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Finding data on disk Each track and sector is labeled

Some are reserved

Listing of where files are stored File Allocation Table (FAT)

FAT32

NTFS

Data is organized in clusters Size of data the OS handles


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DiskettesAlso known as floppy disks

Read with a disk drive

Mylar disk

Spin at 300 RPM

Takes .2 second to find data

3 floppy disk holds 1.44 MB


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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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Optical Storage Devices

CD-ROM Read using a laser

Written from the inside out

CD speed is based on the original Original CD read 150 KBps

A 10 X will read 1,500 KBps

Standard CD holds 650 MB


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6A-13

Optical Storage Devices

DVD-ROM Digital Video Disk

Use both sides of the disk

Capacities can reach 18 GB

DVD players can read CDs


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6A-14

Solid State Devices

Data is stored physically No magnets or laser

Very fast


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6A-15

Solid State Devices

Flash memory Found in cameras and USB drives

Combination of RAM and ROM

Long term updateable storage


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6A-16

USB Pen Drive

1 USB connector

2 USB mass storage controller device

3 Test points

4 Flash memory chip

5 Crystal oscillator

6 LED

7 Write-protect switch

8 Space for second flash memory chip
http://en.wikipedia.org/wiki/Image:Usbkey_internals.jpg


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6A-17

Solid State Devices

Solid-state disks Large amount of SDRAM

Extremely fast

Volatile storage Require battery backups

Most have hard disks copying data


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6A-18

Drive Performance

Average access timeAlso known as seek time

Time to find desired data

Measured in milliseconds Depends on two factors

RPM

Time to access a track

Hard drive between 6 and 12 ms

CD between 80 and 800 ms


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6A-19

Drive Performance

Data transfer rate How fast data can be read

Measured in Bps or bps

Hard drive ranges from 15 to 160 MBps CD ROMS depend on X factor

24x CD transfers 24 x 150 KBps

Floppy disks transfer at 45 KBps


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Chapter 6A & B

End of Chapter

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Intro_Ch_06A_Br