1 Copyright 2003 The McGraw-Hill Companies, Inc. 66 Secondary Storage computing ESSENTIALS.

11Copyright 2003 The McGraw-Hill CompCopyright 2003 The McGraw-Hill Companies, Inc.anies, Inc.

6666Secondary Storage

（辅助存储器）

computing ESSENTIALS

Copyright 2003 The McGraw-Hill CompCopyright 2003 The McGraw-Hill Companies, Inc.anies, Inc.

22

Competencies Competencies （（能力）能力）

Different types of media

Floppy disks

Hard disks

Performance enhancements

Optical disks

Specialized media



33

Secondary Storage Secondary Storage （（辅助存储辅助存储器）器）

• Stores information

• Non-volatile, permanent storage

• Characteristics

– Media

– Capacity

– Access time



44

Types of Storage MediaTypes of Storage Media （（存储介存储介质类型）质类型）

• Types widely used today

– Floppy disks

– Hard disks

– Optical disks

– Magnetic tape



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Floppy DisksFloppy Disks （（软盘）软盘）• Portable and removable• Flat circular Mylar media

– Magnetic charge on metal oxide film coating

• Standard 2HD 1.44 MB• Parts

– Tracks– Sectors



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High Capacity Floppy DisksHigh Capacity Floppy Disks（（高容量软盘）高容量软盘）

• Floppy disk cartridges

– Zip Disks

• 250 MB

– SuperDisks

• 120 MB

– HiFD disks

• 200 MB



77

Hard DisksHard Disks （（硬盘）硬盘）• Metallic disks• Fast retrieval, greater capacity• Read/write heads ride cushion of

air .000001” thick

• Three types

– Internal hard disk

– Hard-disk cartridge

– Hard-disk pack



88



99

Internal Hard DiskInternal Hard Disk （（内置硬内置硬盘）盘）• Inside system unit

• Non-removable or portable

• Great capacity

– Over 100 Gigabytes

• Fast access speed



1010

Hard-disk CartridgesHard-disk Cartridges （（移动硬盘）移动硬盘）

• Portable, removable

• Complement internal

hard drive

– JAZ from Iomega

– SPARQ from

SyQuest

• PC Card Hard Disks

– Laptop computers



1111

Hard-disk PacksHard-disk Packs （（硬盘包）硬盘包）

• Used in mainframes

• Removable

• Multiple read/write

heads

• Massive storage

capacity

• Fast access time



1212

Performance EnhancementsPerformance Enhancements（（性能增强）性能增强）

• Improving performance of hard disks

– Disk caching

– Redundant Arrays of Inexpensive Disks

(RAID)

– File compression and decompression



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• Very large capacity

– Up to 17 gigabytes

• Use reflected light projected by a laser

• Lands and Pits represent 1’s and 0’s

• Formats

– Compact Disk (CD)

– Digital Versatile Disk (DVD)

– DataPlay

Optical DisksOptical Disks （（光盘）光盘）computing ESSENTIALS


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Compact DisksCompact Disks （（光盘）光盘）• Widely used format today• Can store from 650 MB to 1 GB• Rotational speed = data transfer time• Types of CDs

–CD-ROM–CD-R–CD-RW



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CD-ROMCD-ROM （（只读光盘）只读光盘）

• Compact Disc-Read Only Memory

– Cannot be written to or erased

• Similar to commercial music CDs

• Used often to distribute large databases

or references



1616

CD-R & CD-RWCD-R & CD-RW （（可记录光盘和可重写光可记录光盘和可重写光盘）盘）

• CD-Recordable

– Written to once

– Custom made music CDs

• CD-ReWritable

– Erasable CD

– Ideal for multimedia presentations



1717

DVDDVD （（数字化通用光盘）数字化通用光盘）

• Digital Versatile Disk

• Rapidly replacing CDs

– Higher capacity

– 17 times the capacity of a CD



1818

DVD TypesDVD Types （（ DVDDVD 类型）类型）• DVD types

– DVD-ROM• Read only memory

– DVD-R • Recordable

– DVD-RAM or DVD-RW• Competing rewritable formats



1919

DataPlayDataPlay （（超小型光盘）超小型光盘）

• Optical write-once format

• Similar to CD-R

• Size of a quarter

• Used for special applications

– Storing digital photographs

– Storing music for portable players



2020

Other Secondary Storage Other Secondary Storage TypesTypes （（其他辅助存储器类其他辅助存储器类

型）型）• Complement other secondary storage

devices

• Specialized device types

– Magnetic tape

– Internet hard drives

– Solid state storage



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Magnetic TapeMagnetic Tape （（磁带）磁带）

• Sequential access

• Commonly used for backing-up data

• Very large capacity

• Types of magnetic tape

– Tape cartridges

– Magnetic tape reels



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Magnetic Tape TypesMagnetic Tape Types （（磁带类型）磁带类型）

• Tape cartridges

– Backup tape for microcomputer

– Capacities range from 120 MB to 5 GB

– Digital audio tape (DAT)

• Tape reels

– Minicomputer and mainframe

– 1/2 inch wide and 1/2 mile long

– Stores 1600 to 6400 cpi



2323

Internet Hard Drive and Internet Hard Drive and Solid StateSolid State （（网络硬盘驱动器和固态存储网络硬盘驱动器和固态存储

器）器）• Internet hard drive

– Free or low-cost storage on the Web

– Access information from any location

– Access time is greater

• Solid-state storage

– No moving parts

– Flash memory cards



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A Look to the FutureA Look to the Future （（前景）前景）

• Blue laser light optical devices

• Aimed more accurately

• Can increase storage capacity to 27 GB per standard optical disk

• New players will likely play both


1 Copyright 2003 The McGraw-Hill Companies, Inc. 66 Secondary Storage computing ESSENTIALS.

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