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Storage

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Explain the difference between storage systems and memory. ... Flash memory cards CompactFlash, Secure Digital (SD), MiniSD, MultiMedia (MMC) ... – PowerPoint PPT presentation

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Title: Storage


1
Chapter 4
  • Storage

2
Learning Objectives
  • Explain the difference between storage systems
    and memory.
  • Name several general properties of storage
    systems.
  • Identify the two primary types of magnetic disk
    systems and describe how they work.

3
Learning Objectives, Contd.
  • Discuss the various types of optical disc systems
    available and how they differ from each other and
    from magnetic systems.
  • List at least three other types of storage
    systems.
  • Summarize the storage alternatives for a PC,
    including which storage systems should be
    included in all PCs and when the other systems
    would be appropriate.

4
Overview
  • This chapter covers
  • Common characteristics of storage systems
  • Magnetic disk storage systems
  • Optical disc storage systems
  • Other types of storage, such as flash memory,
    magnetic tape, remote storage, and smart cards

5
Properties of Storage Systems Storage Devices
and Media
  • Involve two physical parts a storage device and
    a storage medium.
  • Can be internal (located inside the system unit),
    or external (located outside the system unit).
  • Storage devices are identified by names and/or
    letters (e.g. C for first hard drive).

6
Properties of Storage Systems Non-Volatility
  • Storage media are non-volatile
  • When power to the device is shut off, data stored
    on the medium remains.
  • This is in contrast to most types of memory,
    which are volatile.

7
Properties of Storage Systems Removable vs.
Fixed Media
  • Fixed media typically faster and less
    expensive.
  • Removable media unlimited capacity and can be
    easily transported and secured.

8
Properties of Storage Systems Random vs.
Sequential Access
  • Random access ( direct access ) data can be
    retrieved in any order, independent of its
    physical location (most types of storage media).
  • Sequential access data can be retrieved only in
    the same sequence in which it is physically
    stored (magnetic tape).

9
Properties of Storage Systems Logical vs.
Physical Representation
  • Logical file representation refers to the users
    view of the way data is stored (filename,
    folders, etc.).
  • Physical file representation is the actual
    physical way the data is stored on the storage
    media as viewed by the computer.

10
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11
Magnetic Disk Systems
  • Magnetic disks are the most widely used storage
    medium in computers today.
  • Data is stored by magnetizing particles on the
    storage medium.
  • Two common types
  • Floppy disks
  • Hard disks

12
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13
Floppy Disks and Drives
  • Floppy disk characteristics
  • Typically 3½ inches in diameter.
  • Typically hold 1.44 megabytes.
  • Inserted into floppy disk drive to be read from
    or written to.

14
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15
Floppy Disks and Drives, Contd.
  • Disk is divided into tracks, sectors, and
    clusters.
  • The disks file directory keeps track of the
    contents of the disk so files can be retrieved
    (by filename) at a later time.

16
Floppy Disks and Drives, Contd.
  • Using floppy disks
  • Must be inserted into the proper drive in the
    proper direction.
  • Should not be removed when the disk is being
    accessed.
  • High-capacity removable magnetic disks and drives
  • Zip disks (750 MB)
  • SuperDisks (240 MB)

17
Hard Disk Drives
  • Hard drive characteristics
  • Metal disk onto which data is stored
    magnetically.
  • Disks are usually permanently sealed inside the
    hard driveallows faster speeds and storage of
    more data than removable systems.
  • Can be internal or external.

18
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19
Hard Disk Drives, Contd.
  • Hard drive characteristics, contd
  • Organized into tracks, sections, clusters, and
    cylinders (the collection of tracks located in
    the same location on a set of hard disk
    surfaces).
  • Read/write head doesnt touch the surface of the
    disk.
  • Bumping PC when disk is being accessed or dust or
    other obstacles on a hard-disk system can cause a
    head crash and damage the surface of the disk.

20
Hard Disk Drives, Contd.
  • Disk access time.
  • Factors seek time, rotational delay, data
    movement time
  • Can use multiple partitions.
  • Disk cachestrategy for speeding up system
    performance.
  • Hard drive standards (EIDE, SCSI, Fibre Channel,
    USB) .

21
Hard Disk Drives, Contd.
  • Portable hard drive systems
  • Offer large storage capacities and portability.
  • Either entire drive or just hard disk cartridge
    is transported.

22
Hard Disk Drives, Contd.
  • Storage systems for large computer systems and
    networks
  • Storage servers containing racks of hard drives.
  • Network attached storage (NAS).
  • Storage area networks (SANs).
  • RAID (for increased performance and/or fault
    tolerance).

23
Optical Disc Systems
  • Laser beams write and read data packed at very
    tight storage densities, many times finer than
    that of a typical magnetic disk.
  • Are typically 4½-inch discs, but can be a variety
    of shapes and sizes.
  • Data is stored optically on a continuous spiral
    track.
  • Can be CDs or DVDs.

24
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25
Read-Only Discs CD-ROM and DVD-ROM Discs
  • CD-ROM discs cannot be written to or erased and
    typically hold 650 MB (e.g. music CDs).
  • DVD-ROM discs are similar to CD-ROM discs, but
    have higher capacity of 4.7 GB to 17 GB (e.g.
    movie DVDs).
  • Data is stored by burning pits into the disc
    surface that can be read using a laser beam.

26
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27
Recordable Discs CD-R, DVD-R, and DVDR Discs
  • Recordable discs can be written to, but not
    erased or rewritten.
  • Burning a CD or DVD permanently records data onto
    the disc.
  • CD-R discs are commonly used to store data and
    for custom music CDs.
  • DVD-R/DVDR discs are commonly used for home
    movies and other high-capacity applications.

28
Rewritable Discs CD-RW, DVD-RW, DVDRW, DVD-RAM,
and Blue Laser Discs
  • Rewritable discs can be used in the same way as
    magnetic disksdata can be stored and erased as
    needed.
  • Phase-change technology is used to record data
    onto the disc using reflectivity.
  • Rewritable discs can be erased by reverting the
    reflectivity back to the original state.
  • Blue laser discs are an emerging higher-capacity
    (23.3 GB) form of optical disc.

29
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30
Other Types of Storage Systems
  • Magneto-optical discs
  • A combination of magnetic and optical technology.
  • Can store up to 9.1 GB per disk.

31
Other Types of Storage Systems, Contd
  • Flash memory media
  • Chip-based storage.
  • Solid state storage systemhas no moving parts,
    so are more shock-proof and portable than
    conventional storage systems.
  • Commonly used with digital cameras, digital music
    players, handheld PCs, notebook computers, smart
    phones, etc.

32
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33
Other Types of Storage Systems, Contd
  • Flash memory media, contd.
  • Common forms of flash memory
  • Flash memory sticks.
  • Flash memory cardsCompactFlash, Secure Digital
    (SD), MiniSD, MultiMedia (MMC), SmartMedia, and
    xD Picture cards.
  • Flash memory drives, such as USB flash drives.

34
Other Types of Storages Systems, Contd
  • Magnetic tape systemsplastic tape that is
    magnetized to represent data.
  • Used primarily for backup and archival purposes
    (sequential access only).
  • Read from and written to via a tape drive.
  • Most tape media are in the form of cartridge
    tapes, though detachable-reel tapes exist as
    well.  

35
Other Types of Storage Systems, Contd
  • Remote storagestorage devices that are not
    directly connected to your PC.
  • Network storageaccessible through a local
    network.
  • Online storageaccessible via the Internet and
    used for backup, as well as to transfer files to
    others.

36
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37
Other Types of Storage Systems, Contd
  • Smart card credit-card-sized piece of plastic
    that contains some type of computer circuitry.
  • Holds less than a few megabytes.
  • Commonly used to store prepaid amounts of digital
    cash or personal information.
  • Smart card readers are attached to a PC or built
    into a cell phone, keyboard, or other device.

38
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39
Other Types of Storage Systems, Contd
  • Holographic storage
  • Uses multiple laser beams to store data in three
    dimensions.
  • Stores data in page format.
  • No moving parts and simultaneous access to all
    data on a page.

40
Comparing Storage Alternatives
  • Factors to consider speed, expense, portability,
    storage capacity, and compatibility.
  • Most PC users require
  • Hard drive
  • CD or DVD drive
  • Floppy drive
  • Additional devices (flash memory card reader,
    etc.) as needed for the devices being used in
    conjunction with the PC (e.g. digital camera)

41
Summary
  • Properties of storage systems
  • Magnetic disk systems
  • Optical disc systems
  • Other types of storage systems
  • Comparing storage alternatives
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