College of Computer and Information Science

Chapter 8

Secondary Storage

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Key Words & Terms• access speed: 读写速度 • Blu-Ray (BR): 蓝光• capacity: 容量• CD (compact disc): 紧凑格式盘• CD-R (CD-recordable): 可写 CD （一次）• CD-ROM (compact disc-read only memory): 只读 CD • CD-ROM jukebox: CD-ROM 光盘库• CD-RW (compact disc rewritable): 可擦写 CD （多次）• cylinder: 柱面• density: 密度• direct access: 直接读写• disk caching: 磁盘高速缓冲• DVD (digital versatile disc or digital video disc): 数字式通用盘• DVD player: DVD 播放器• DVD-R or DVD+R (DVD recordable): 一次性刻录格式• DVD-RAM (DVD-random-access memory): 可读写 DVD

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Key Words & Terms• DVD-ROM (digital versatile disc-read only memory): 只读 DVD• DVD-RW or DVD+RW (DVD rewritable): 可擦写 DVD• enterprise storage system: 大型存储系统• Erasable optical disk: 可擦写光盘 • file compression: 文件压缩 • file decompression: 文件解压 • file server: 文件服务器• flash memory card: 闪存卡 • floppy disk: 软盘• floppy disk cartridge: 大容量软盘 • floppy disk drive (FDD): 软盘驱动器• hard disk: 硬盘 • hard-disk cartridge: 移动式硬盘 • hard-disk pack: 硬盘盘组• HD DVD (high-definition DVD): 高清 DVD• head crash: 读写头损坏 • hi def (high definition): 高清

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Key Words & Terms• magnetic tape: 磁带• magnetic tape reel: 磁带卷• magnetic tape streamer: 流式磁带• mass storage: 海量存储• mass storage devices: 海量存储设备 • media: 介质• optical disk: 光盘• optical disk drive: 光盘驱动器 • organizational Internet storage: 高速网络存储• PC Card hard disk: PC 卡式硬盘 • pit: 光盘凹陷处• primary storage: 主存• RAID system: 冗余阵列盘系统

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Key Words & Terms• redundant arrays of inexpensive disks (RAID): 冗余阵列

盘• secondary storage: 辅助存储器• secondary storage device: 辅助存储设备• sector: 扇区• sequential access: 顺序读写• shutter: 磁盘读写口 • software engineer: 软件工程师• solid-state storage: 固态存储器• storage devices: 存储设备• tape cartridge: 磁带盒• tape library ：磁带库• track: 磁道• USB drive: USB 驱动器• write-protection notch: 写保护口

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Competencies (Page 1 of 2)

• Distinguish between primary and secondary storage

• Describe the traditional floppy disk and compare it to high capacity floppy disks

• Compare internal hard disks, hard-disk cartridges, and hard-disk packs

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Competencies (Page 2 of 2)

• Describe ways to improve hard-disk operations, including disk caching, redundant arrays of inexpensive disks, and data compression and decompression

• Discuss the different types of optical disks• Describe solid-state storage, Internet drives, and

magnetic tape• Discuss mass storage and mass storage devices

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College of Computer and Information Science 8-8

Introduction

Data storage has expanded from text and numeric files to include digital music files, photographic files, video files, and much more. These new types of files require secondary storage devices with much greater capacity than floppy disks. In this chapter, you will learn about the many types of secondary storage devices including their capabilities and limitations.

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Storage

• Primary storage– Volatile storage– Temporary

storage

• Secondary storage– Nonvolatile storage– Permanent storage

• Secondary storage characteristics – Media– Capacity– Storage devices– Access speed

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Secondary Storage Devices

• Most desktop microcomputer systems have floppy disks, hard disks, and optical disk drives

• Are used to save, back up, and transport data files and programs

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Floppy Disks

• Portable or removable storage media• Typically used to store and transfer small

word processing, spreadsheet, and other types of files

• Floppy disk drives (FDD)– Store data and programs– Retrieves data by reading electromagnetic

charges– Also called flexible disks and floppies

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Traditional Floppy Disk

• Most common type is 2HD “two-sided, high-density”

• Attributes– Shutter– Labels– Write-protection notch– Tracks– Sectors

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High Capacity Floppy Disks

• Known as a floppy-disk cartridge• Require special disk drives• Most widely used is the Zip disk

– 100 MB, 250 MB or 750 MB capacity– Used to store multimedia, database, large text,

and spreadsheet files

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College of Computer and Information Science 8-14

Hard Disks• Use thicker, metallic platters for storage• Faster than a floppy diskette• Large capacity• Sensitive instruments • There are three types of hard disks:

– Internal Hard Disk– Hard-disk cartridge– Hard-disk pack

• Performance Enhancements

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Materials that Cause a Head Crash

• Head crash is a disaster for a hard disk

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Internal Hard Disk

• Located inside system unit

• Designated as the C drive

• Advantages over floppies

– Capacity

– Access speed

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Hard-Disk Cartridges

• Removable hard disks

• Used to complement

internal hard disk

• Capacities of 20 to 100 GB

• Iomega is one of the most

widely used

PC Card Hard Disks

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Hard-disk cartridge

Return

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Hard-Disk Packs

• Removable hard disk

• Massive storage capacity

• Common in mainframes

• Are utilized by banks and credit card companies

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Performance Enhancements

• Disk caching

• Redundant arrays of inexpensive disks (RAID)

• File compression and decompression

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Optical Disks

• Hold over 50 gigabytes of data• Attributes

– Lands– Pits

• Three types– Compact Disc (CD)– Digital Versatile Disc (DVD)– Hi-Def Disc

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Compact Disc

• Optical format• From 650 MB to 1 GB capacity• Rotation speeds vary • Three basic types

– Read only: CD-ROM– Write once: CD-R– Rewriteable: CD-RW

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Digital Versatile Disc

• Digital Versatile Disc or Digital Video Disc (DVD)

• Similar to CDs, but can store more data• Three basic types

– Read only: DVD-ROM– Write once: DVD+R; DVD-R– Rewritable: DVD+RW; DVD-RW; DVD-RAM

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High-Definition Disc

• Next generation of optical disc• Far greater capacity than DVDs• Three basic types

– Read only– Write once– Rewriteable

• Two competing hi def formats– HD DVD– Blu-Ray

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Other Types of Secondary Storage

• Solid-state storage

• Internet hard drives

• Magnetic tape

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Ipods and Music From The Internet

• The Internet can be used as a medium to locate and play music

• A user can create compact discs, or transfer music to a portable player

• Requirements– Software– Hardware– Internet

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Solid-State Storage

• Flash memory cards– Widely used in notebook computers– Used to record MP3 music files

• USB drives – Key ring flash memory

devices or flash drives– Connects to a USB port

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Key ring flash memory

Flash memory card

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Internet Hard Drives

• Known as i-drive or online storage• Low cost and can access information from

any location using the Internet• Oriented to either businesses or individuals

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Magnetic Tape

• External storage• Provides sequential access

– Information stored in sequence – Slower than disks which provide

direct access

• Magnetic tape streamers or tape cartridges used by both mainframes and microcomputers

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Mass Storage Devices

• Mass storage refers to the tremendous amount of secondary storage required by large organizations

• Mass storage devices are specialized high-capacity secondary storage devices

• Enterprise storage system

promotes efficient and safe

use of data across networks

within organizations

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Discussion Questions (Page 1 of 2)

• Discuss the traditional and high-capacity floppy disks.

• What are the three types of hard disks? Describe three ways to improve hard disk performance.

• What are the two most common optical disk formats? What is hi def? Describe the basic types for each format.

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Discussion Questions (Page 2 of 2)

• Discuss solid-state storage, Internet hard drives, and magnetic tape. What are the advantages and disadvantages of each?

• Discuss mass storage, enterprise storage systems, and mass storage devices.

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Crossword Puzzle Answers:

Across

Num. Clue Answer

5 Improves hard-disk performance by anticipating data needs.

Disk caching

6 Web-based storage. Internet drive

7 Invisible wedge-shaped division of a track.

Sector

8 Portable and removable storage device.

Floppy

10 Runs through each track of a stack of platters.

Cylinder

11 How tightly the bits can be packed next to each other.

Density

Down

Num. Clue Answer

1 Ring of concentric circles without visible grooves.

Track

2 Grouped disk drives treated as one hard disk by the computer system.

RAID

3 Measures the amount of time required to retrieve data.

Access time

4 Represent 1s and 0s. Pits and lands

9 Disk with 500 times the storage as a standard floppy.

Zip

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Answers for Multiple Choice and Matching

Num Multiple Choice Answers Matching Answers

1 A G

2 A A

3 C J

4 A I

5 C D

6 A B

7 C H

8 D C

9 D F

10 C E

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End of Chapter 8