Secondary storage (NHẬP môn điện TOÁN SLIDE)

Chapter 08: Secondary
Storage

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Competencies (Page 1 of
2)

• Distinguish between primary and secondary
storage
• Discuss the important characteristics of
secondary storage, including media,
capacity, storage devices, and access speed
• Describe hard disk platters, tracks, sectors,
and head crashes
• Compare internal and external hard drives
• Discuss performance enhancements
including
disk caching, RAIDs, file compression, and
file decompression

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Competencies

(Page 2 of

2)

• Define optical storage including compact,
digital versatile, and high-definition discs
• Define solid-state storage, including solidstate drives, flash memory, and USB drives
• Define cloud storage and cloud storage
services
• Discuss mass storage devices, enterprise
storage systems, and storage area
networks

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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.
• In this chapter, you 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
– Random Access
Memory (RAM)

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• Secondary storage
– Nonvolatile storage
– Permanent storage

ã Secondary storage
characteristics





Media
Capacity
Storage devices
Access speed

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Secondary Storage
Devices
• Provides permanent or
nonvolatile storage
• Data and programs can be
retained after the computer
has been shut of
• Most desktop microcomputer
systems have both hard and
optical disk drives

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Hard Disks
• Use rigid, metallic platters for
storage
• Files organized using tracks, sectors,
and cylinders

• Large capacity (terabytes)
• Sensitive instruments
• Two types of hard disks:
– Internal Hard Disk
External Hard Disks

ã Performance enhancements

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Materials that Cause a Head
Crash
• A head crash is a disaster for a
hard disk, not to mention the
data stored on the disk

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Internal Hard Disk
• Located inside system unit and
often designated as the C: drive
• Used to store programs and data
files
• Advantages over removable
media
– Capacity
– Access speed

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External Hard Disks
• Removable hard disks
• Used to complement internal hard
disk with an unlimited amount of
additional storage
ã Capacities extend into the terabytes
(TBs)

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Performance
Enhancements
• Disk caching to improve
hard disk performance
• Redundant arrays of
inexpensive disks (RAID)
to expand storage and
to improve access speed
ã File compression
and

decompression
to increase capacity

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Optical Disks
• Hold over 100 gigabytes (GB) of data
• Attributes
– Lands
– Pits

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

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Compact Disc (CDs)
• Optical format
• Capacity of 650 MB to 1 GB
• Rotation speeds vary
• Three basic types
–
–
–

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Read only (CD-ROM)
Write once (CD-R)
Rewriteable (CD-RW)

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Digital Versatile Discs
(DVDs)
• Like CDs, but newer format called
digital versatile disc or digital
video disc (DVD)
• Capacity of 4.7 GB to 17 GB
• Three basic types
– Read only
(DVD-ROM)
– Write once
(DVD+R and DVD-R)
– Rewriteable
(DVD+RW, DVD-RW, and DVD-RAM)

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Blu-ray Disc (BDs)

• Next generation optical disc for
recording high-definition (hi def)
video
• Capacity of 25 GB to 100 GB
• Blu-ray optical drives are usually
capable of reading standard
DVDs and CDs in addition to Bluray discs

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Solid-State Storage
• Solid–state drives (SSDs)
– Faster and more durable
• Flash memory cards
– Widely used in computers,
cameras, and portable
devices such as mobile
phones
• USB Drives (or Flash Drives)
– Compact and easily

transported
– Capacity of 1 GB to 256 GB

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Making IT Work for You
Flash Camcorders, YouTube, and
MySpace
• Flash-based camcorders have made
creating digital video simpler and
more afordable
• Easily upload your creations to photoand
video-sharing Web sites on the
Internet

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Cloud Storage
• Cloud computing is where the
Internet
acts as a “cloud” of servers
– Applications provided as a service rather
than a product (for example, cloud or
online storage)

• Cloud storage services
make it easy to
upload and share
files with anyone

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Mass Storage Devices

• Organizations require tremendous
amounts of secondary storage called mass
storage
• Enterprise storage systems ensure data
security using specialized strategies and
devices, such as
–
–
–
–
–
–

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File servers
Networked attached storage (NAS)
RAID systems
Tape libraries
Organizational cloud storage
Storage Area Network (SAN)
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Enterprise Storage
Systems

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Careers In IT
• Software engineers analyze users’
needs and create application
software
• General employer requirements
– Bachelors degree in
computer science
– Extensive knowledge of
computers and technology
– Communication and analytical skills

ã Annual salary of $63,000 to $98,500

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A Look to the Future

Your Entire Life Recorded on a Single Disk

• Future secondary storage disks
will eventually store terabytes
(TB) or petabytes (PB)
– Your entire life captured in
digital video on a single disc
– Currently developing programs
that can scan photos and videos
for a particular person’s face

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Open-Ended
Questions(Page 1 of 2)
• What are the two types of hard disks?
Describe three ways to improve hard
disk performance.
• Compare solid-state and hard disk
storage.
• List and compare the three most
common optical disc formats?

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Open-Ended Questions
(Page 2 of 2)
• Describe cloud computing and cloud
storage.
• Discuss mass storage systems
including enterprise storage systems
and storage area networks.

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