Storage

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Lecture 6

• Storage

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Storage

• Storage medium place or area where the data is
  actually stored
• Storage device system that places information
  on and reads information from the storage medium

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Storage

• Fixed media devices have their storage media
  sealed in the device so it cannot be removed
• Hard drives
• Removable media devices allow the user to remove
  the storage media and replace it
• Floppy Drive, CD ROM

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Storage

• Fixed advantages
• Reliable
• High speed

• Removable advantages
• Portable
• Security
• Unlimited capacity

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Storage

• Storage is typically measured in terms of bytes,
  similar to memory
• KB
• MB
• GB

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Storage Media

• Types
• Magnetic
• Optical
• Flash
• Holographic

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Magnetic Media

• Magnetic Storage Devices
• Floppy discs
• Tape Drives
• Hard Drives
• Zip discs

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Magnetic Media

• Information is stored by magnetic particles
• Particles alignment represents one or zero
• and -

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Magnetic Media

• Read/Write head device or object that uses
  magnets and magnetic forces to align the
  particles on a disc surface to represent binary

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Line Magnetic Media

• Example Tape drives
• Tape drives use what we call sequential access
• the data can only be retrieved in the order
  which it is physically stored on the medium
• Tape cassettes store data and information

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Line Magnetic Media

• Good for backup of servers and files
• Easy to store large amount of data in a secure
  location
• If you want to restore old files with a backup,
  you typically write over the current files
• Therefore sequential access is not a problem

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Circular Magnetic Media

• Typically random or direct access
• data can be retrieved directly from any location
  on the medium, in any order
• This is the kind of access most of us are
  familiar with

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Circular Magnetic Media

• Track Circular rings on the discs surface
• Sectors pie shaped wedges of the disc surface
• Cluster portion of a track within a sector

Track
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Circular Magnetic Media

• Hard drives, Floppy discs, and Zip discs contain
  circular magnetic media
• The media is read while it is spinning
• A magnetic head determines the orientation of the
  particles as the media spins by
• Translated to 1 or 0

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Floppy and Zip discs

• In recent years, these were the main type of
  removable storage media
• Both are quickly becoming obsolete
• Media is stored in plastic cases
• Floppy 3.5 diameter, 1.44MB space
• Zip disc vary from company to company
• Similar in size, but higher capacity

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Hard Drives

• Actual name hard disc drive
• High density magnetic media
• Contain multiple metal discs sealed in the drive
• Read/write heads for each disc

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Hard Drives

• Cylinder the collection of one particular
  track on each disc surface
• Often related data is stored on the same or
  adjacent cylinders
• Minimizes disc access time

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Hard Drives

• Read/Write heads on hard drives have very little
  clearance from the disc surface
• Less than one millionth of an inch
• The gap is more than 5000 times smaller than a
  dust particle
• Hard drives rotate at high speeds
• Thousands of RPMs

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Hard Drives

• Because of the small gap between heads and discs
  and the high disc velocity, the disc surface must
  be completely clean
• Hard drives are assembled in a clean room where
  there is no foreign material
• Workers wear completely enclosed suits

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Hard Drives

• The term hard drive crash comes from the
  read/write head crashing into a small object on
  the disc surface at high speed
• This is not the only reason a hard drive fails
• Just one of the more common reasons
• Keep info on the hard drive backed up often!!!!!

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Hard Drives

• Disc caching storing data or programs that
  might be needed soon in the RAM
• Strategy used by most hard drives to speed up
  performance
• Disc cache area in the RAM designated for
  caching

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Optical Disc

• Lands and Pits represent ones and zeros
• Instead of magnetic particles these discs use
  lasers to read and create what can be interpreted
  as binary
• Best examples are CDs and DVDs

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Optical Disc

• Land parts of the disc that arent changed
• Pits tiny depressions burned into the discs
  surface
• High intensity lasers burn pits into the disc so
  they can later be read by low intensity discs

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Optical Disc

• Data on optical disks is grouped a little
  differently than magnetic disks
• Track the long spiral that starts at the center
  of the disk and spirals out to the edge
• Sector a portion of the long spiral

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Optical Disc

• Compact disc (CD)
• One of the first Optical Disc media
• 600MB to 1GB
• About one half an hour of quality video
• Digital Versatile Disc (DVD)
• 4.7GB up to 17GB
• Several hours of quality video

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Optical Disc

• The track for a DVD is longer, narrower and
  tighter than that of a CD
• Therefore more data can be stored on a DVD
• Cannot be read by the same laser

DVD
CD
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Flash Media

• No moving parts
• Consist of chips and circuitry
• Resistant to shock and vibration
• Minimal power consumption
• Note Flash media is also used to describe some
  animated web content, here we are talking about
  storage media

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Flash Media

• Flash media cards, sticks, etc. are used in a
  variety of devices
• The cell phone in your pocket or purse, likely
  has some sort of flash media storage
• Other devices include PDAs, Digital Cameras, MP3
  players

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Flash Media

• Flash drives
• Storage devices that consist of flash memory
  media and the drive hardware necessary to write
  to and read from that media
• Usually USB or Firewire

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Flash Media

• RFID Radio Frequency Identification
• Becoming a viable way of keeping track of
  inventory
• Currently in testing phases with large retail
  chains
• Endless possibilities

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RFID how it works

• Information is stored on Flash media in a small
  chip
• Long copper coil acts as antenna
• Power from readers energizes tag
• Information extracted through radio transmission

Information
Power
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Holographic Media

• 3D storage system
• Uses multiple lasers to read and store data in
  three dimensions
• Data stored in a page format
• Entire page of data retrieved at one time

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Holographic Media

• Still in the testing phase
• At some point in time may replace the hard drive
• High speed retrieval of large amounts of data

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Holographic Media

• Some companies are set to release holographic
  storage devices as early as the end of the year
• Capable of storing 63 times the information on a
  DVD in a disc the same size (300 GB)