Lecture 3

• Storage medium


  The physical material on which a computer keeps data, information, programs, and applications

  
• Cloud storage


  Keeps information on servers on the Internet, and the actual media on which the files are stored are transparent to the user
• Storage device


  The hardware that records and/or retrieves items to and from storage media
• Capacity


  The number of bytes a storage medium can hold
• Terms used to define storage

  • Kilobyte (KB)
  • Megabyte (MB)
  • Gigabyte (GB)
  • Terabyte (TB)
  • Petabyte (PB)
  • Exabyte (EB)
  • Zettabyte (ZB)
  • Yottabyte (YB)
• Volatile


  • Contents disappear when power is removed (e.g. screen display, most RAM)
• Nonvolatile


  • Contents remain when power is off (e.g. storage)
• Access time


  The amount of time it takes a storage device to locate an item on a storage medium, and the time required to deliver an item from memory to the processor
• Memory vs Storage


  Memory is faster than storage but is expensive and not practical for all storage requirements. Storage is less expensive but is slower than memory.

  
• Hard disk


  Contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information
• Hard disk characteristics


  • Tracks
  • Sectors
  • Platters
  • Form factor
  • Read/write head
  • Revolutions per minute
• Head crash occurs when a read/write head touches the surface of a platter
• Always keep a backup of your hard disk
• SSD (solid state drive)

  A flash memory storage device that contains its own processor to manage its storage
• Advantages of SSD over traditional hard disks

  • Faster access times
  • Faster transfer rates
  • Quieter operation
  • More durable
  • Lighter weight
  • Less power consumption
  • Less heat generation
  • Longer life
  • Defragmentation not required

  
• External hard drive


  A separate freestanding storage device that connects with a cable to a USB port or other port on a computer or mobile device
• RAID (redundant array of independent disks)


  A group of two or more integrated hard drives
• Types of memory cards

  • SDHC
  • SDXC
  • miniSD
  • microSDHC
  • microSDXC
  • CF
  • xD Picture Card
  • Memory Stick

  
• External hard drives


  • Portable storage connected to a computer or mobile device
• RAID


  Redundant array of independent disks - a group of two or more integrated hard drives
• Types of memory cards

  • SDHC
  • SDXC
  • miniSD
  • microSDHC
  • microSDXC
  • CF
  • xD Picture Card
  • Memory Stick PRO Duo
  • M2

  
• How an SD card works


  1. Inserted into a slot

  2. Accessed by the device
• USB flash drives


  Plug into a USB port on a computer or mobile device
• Cloud storage


  An Internet service that provides storage to computer or mobile device users
• Optical discs


  • Flat, round, portable discs made of metal, plastic, and lacquer
  • Written and read by a laser
• How a laser reads data on an optical disc

  1. Laser focuses on track

  2. Reflects off disc

  3. Detected by sensor
• Optical disc data storage

  • Single track that spirals from center to edge
  • Track divided into evenly sized sectors
• Types of optical discs

  • CD-ROM (read-only)
  • CD-R (write once)
  • CD-RW (erasable)
• Types of DVDs


  • DVD-ROM (read-only)
  • DVD-R/DVD+R (write once)
  • DVD-RW/DVD+RW/DVD+RAM (rewritable)
• Enterprise storage


  • Devices intended for heavy use, maximum efficiency, and maximum availability
  • RAID duplicates data to improve reliability
• RAID level 1 (mirroring)


  Backup disk exists for each drive
• Network Attached Storage (NAS)


  Server on a network providing storage to users, computers, and devices
• Storage Area Network (SAN)

  High-speed network providing centralized storage for servers
• Tape storage


  • Magnetically coated plastic ribbon capable of storing large amounts of data
  • Tape drive reads and writes data
• Magnetic stripe card


  Contains information in a magnetic stripe
• Smart card


  Stores data on an integrated circuit embedded in the card
• RFID tag


  Antenna and memory chip that transmits information via radio waves
• NFC-enabled device


  Contains an NFC chip to communicate with NFC tags
• Summary of storage options

  • Hard disks
  • SSDs
  • External hard drives
  • RAID
  • Portable flash memory
  • Cloud storage
  • Optical discs
  • Enterprise storage
  • Magnetic stripe cards
  • Smart cards
  • RFID tags
  • NFC chips and tags