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10/5: Data storage concepts. What is data storage? Types of storage magnetic, optical, magneto-optical, solid state Storage characteristics Magnetic storage: Floppy disks Hard disk drives Optical storage: CD-ROMs, etc. DVDs, etc. Data storage: what is it?.

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10/5: Data storage concepts


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10 5 data storage concepts
10/5: Data storage concepts
  • What is data storage?
  • Types of storage
    • magnetic, optical, magneto-optical, solid state
  • Storage characteristics
  • Magnetic storage:
    • Floppy disks
    • Hard disk drives
  • Optical storage:
    • CD-ROMs, etc.
    • DVDs, etc.
data storage what is it
Data storage: what is it?
  • Long-term storage, not immediate memory
  • Not RAM (short-term memory)
  • Synonyms: secondary storage, auxiliary storage, mass storage

images courtesy of dalelabs.com,, iomega.com, imation.com,

data storage where is it
Data storage: where is it?
  • Storage involves 2 parts: the device & the media
  • Removable vs. fixed media
  • Where can you store data?
    • magnetic media
    • optical media
    • magneto-optical media
    • solid state media

image courtesy of How Computers Work

storage characteristics
Storage characteristics
  • Random vs. sequential access
  • Tracks & sectors
  • Speed
    • spin rate (RPM)
    • seek time & latency
    • access time
    • data transfer rate
  • Storage Capacity
    • areal density
    • size

Image courtesy of How Computers Work

magnetic data storage
Magnetic data storage
  • Use magnets to store bits:
    • example: 0 = N , 1 = S
  • Reading and writing
  • Floppy disk drives
  • Hard disk drives

PACE

image courtesy of How Computers Work

floppy disk drives types
Floppy disk drives: types
  • Low-density floppy drives: 5.25” floppy disks3.5” 1.44 MB floppy disks
  • High-density floppy drives: Zip disks, LS-120 disks

Images courtesy of How Computers Work, Imation.com, and Iomega.com

floppy disk drives how they work
Floppy disk drives: how they work
  • Shutter opens with an arm.
  • Cookie spins on the spindle.
  • Read/write heads get close to the cookie inside
  • Magnetic particles generate electric currents in the heads.
  • Electric currents are interpreted as a series of bits.

Images courtesy of How Computers Work

hard disk drives overview
Hard disk drives: overview
  • Glass platters coated with magnetic particles
  • Read/write heads like floppy drives but much smaller
  • Multiple platters, multiple heads.

Image courtesy of How Computers Work

hard disk drives how they work
Hard disk drives: how they work
  • Platters spin on the spindle.
  • Heads move over the platters.
  • To read, magnetic particles generate currents in the heads.
  • Electric currents are interpreted as a series of bits.
  • To write, the electric currents manipulate the magnetic particles on the platters.

Images courtesy of How Computers Work

optical storage
Optical Storage
  • Instead of using magnetism to store bits, we use light
  • A laser is the light
    • Laser: “light amplification by stimulated emission of radiation”
    • Extremely focused, narrow beam of powerful light
    • Depending on the wavelength, the beam can be narrower or wider
  • Lands are flat areas on the disc
    • Reflect light like a mirror
  • Pits are holes in the disc
    • Scatter light

Courtesy of http://www.microserve.net/~tpetchy/DVD.shtml

cd drives types and operation
CD Drives: Types and Operation
  • CD-ROM drive speeds: how many times faster than the original CD-ROM drives
    • 2x, 4x, 6x, 8x, 16x, 32x, 48x
  • Operation:
    • Diode generates laser
    • Laser bounces off mirrors, reaching the disc
    • Disc reflects or scatters laser
    • Light-sensing diode sees the reflections, comparing them to a timing circuit to generate 0s and 1s

Image courtesy of c-cube.com

types of optical discs
Types of Optical Discs
  • Compact discs:
    • CD-ROM: read only memory (680 MB)
    • CD-R: Recordable (650 MB)
    • CD-RW: ReWritable (495 MB)

Image courtesy of c-cube.com

types of optical discs1
Types of Optical Discs
  • Digital versatile discs – higher density storage
    • DVD-ROM: read only memory (4.7 – 17 GB)
    • DVD-R: Recordable (3.9 GB?)
    • DVD-ram (5.2 GB) & DVD+RW (6.0 GB): Rewritable (still fighting)

Image courtesy of c-cube.com