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Processing. Input. Output. Internal Memory. Secondary Storage. Secondary Storage. used to permanently store data and programs. Physical Parts. storage device diskette drive hard-disk drive optical disk drive tape drive storage medium magnetic disks, tapes optical disks.

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PowerPoint Slideshow about 'Secondary Storage' - affrica


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Processing

Input

Output

Internal

Memory

Secondary Storage


Secondary storage

Secondary Storage

used to permanently store data and programs


Physical parts
Physical Parts

  • storage device

    • diskette drive

    • hard-disk drive

    • optical disk drive

    • tape drive

  • storage medium

    • magnetic disks, tapes

    • optical disks


Magnetic disks
Magnetic Disks

  • disks covered with a thin layer of ferrous oxide

  • data is stored as magnetized fields on the disk

  • most widely used secondary storage medium

  • diskettes, zip disks, jaz disks, superdisks, hard disks


Diskettes
Diskettes

  • flexible plastic disks encased in a plastic jacket

  • sizes:

    • 3 1/2 inch

    • 5 1/4 inch

  • densities:

    • low or double density

    • high density


Diskette data storage
Diskette data storage

  • data are stored and accessed at a unique disk address

  • formatting a diskette divides it into addressable storage locations

    • tracks

    • sectors

    • file directory (file allocation table)


The Surface of a Disk

  • Track

  • Sector

  • Cluster


Disk drive
Disk Drive

  • rotates the disk

  • a read/write head accesses the tracks through the recording window

    • direct access device

  • disk drives are specific to the size and density of the diskettes


Uses for diskettes
Uses for Diskettes

  • transferring small amounts of data between computers

  • doing small amounts of backup

  • software distribution

  • Other considerations:

    • very portable

    • comparatively slow access to data

    • inexpensive

    • diskettes are subject to damage


Hard disks
Hard Disks

  • metal disks (platters) covered with ferrous oxide

  • disk pack

    • set of disks on a mounting shaft

    • access mechanism containing the read/write heads

    • circuit board

    • sealed in an airtight unit


Hard disks cont
Hard Disks (cont.)

  • direct access device

  • fast data access

  • large storage capacity

    • 4 to 36 gigabytes or more

  • Smart 2 Ultra ATA/66


Zip drives and disks
Zip Drives and Disks

  • internal or external drive

  • stores:

    • 100 MB on a single disk

    • 250 MB

  • reasonable cost


Jaz drives and disks
Jaz Drives and Disks

  • stores 1 or 2 GB per disk

  • internal or external

  • fast access to data


Imation ls 120 super disk drive and superdisks diskettes
Imation LS-120 Super Disk Drive and SuperDisks Diskettes

  • SuperDisks store 120 MB of data

  • SuperDisk Drive reads and writes both the SuperDisk diskette and conventional 3.5” 1.44 MB diskette


Magnetic tape
Magnetic Tape

  • data is stored on a mylar tape coated with ferrous oxide

  • typically used to backup file servers

  • sequential access

  • common types:

    • 4mm/8mm DAT tapes

    • DDS

    • DLT tapes


Optical storage media
Optical Storage Media

  • data is stored by burning tiny holes in the surface of a optical disk with a laser beam

  • very large storage capacity (several GB of data on a optical disk)

  • media of choice for software distribution

  • good for storing multimedia data


Types
Types

  • CD-ROMS

    • most common

    • used extensively for software distribution

    • access times dependent on the speed of the CD-ROM disk drive (24x, 32x, 40x)

  • CD-R

  • CD-RW

    • 8x4x20x means 8x record, 4x rewrite, 20x read

  • DVD


Factors to consider when comparing types of storage
Factors to consider when comparing types of storage:

  • Internal vs. external design

  • media capacity

  • portability

  • access to data

    • speed

    • read/write capability

    • type (sequential or direct)

  • cost


Disk controllers
Disk Controllers

  • IDE, EIDE, Ultra IDE

  • SCSI, SCSI wide, SCSI ultrawide, Ultra 2 SCSI


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