ch7

• Primary storage


  Volatile storage, loses content when the computer loses power, temporary storage
• Secondary storage


  Nonvolatile storage, stores programs and data regardless of power, permanent storage
• Secondary storage characteristics


  • Media
  • Capacity
  • Storage devices
  • Access speed
• Writing


  Process of saving information to storage
• Reading


  Process of accessing information from storage
• Hard disks


  Save files by altering the magnetic charges of the disk's surface to represent 1s and 0s
• Hard disks


  • Use rigid, metallic platters that are stacked one on top of one another
  • Store and organize files using tracks, sectors, and cylinders

  
• Head crash


  Occurs when read-write head makes contact with the hard disk's surface or with particles on its surface
• Internal hard disk


  Located inside the system unit, used to store programs and data files
• External hard drive


  Removable, used to complement internal hard disk, used to back up the contents of the internal hard disk

  
• Disk caching


  Uses hardware and software to anticipate data needs, performs function similar to RAM caching, improves processing by acting as a temporary high-speed holding area between a secondary storage device and the CPU
• RAID


  Linked, inexpensive hard-disk drives
• File compression


  Reduces file size
• File decompression


  Expands compressed files
• Solid-state storage


  Devices have no moving parts
• Solid-state drives


  Faster and more durable than hard disks
• Flash memory cards


  Widely used in laptops, smartphones, GPS navigation systems

  
• USB Drives (or Flash Drives)


  Connect to USB port, capacity of 1 GB to 256 GB, portable

  
• Optical discs


  Use reflected light to represent data, lands represent 1s and 0s, pits are bumpy areas that determine the 1s and 0s
• Optical disc formats


  • CD (700 MB)
  • DVD (4.7 GB)
  • BD (50 GB)
• Optical disc types


  • ROM (read only-memory)
  • R (recordable)
  • RW or RAM (rewritable or random-access memory)

  
• Cloud computing


  The Internet acts as a "cloud" of servers, applications provided as a service rather than a product
• Cloud storage


  Provided by servers that provide cloud storage or online storage
• Mass storage


  Tremendous amount of secondary storage required by large organizations
• Mass storage devices


  Specialized high-capacity secondary storage devices designed to meet organizational demands for data storage
• Enterprise storage system


  Strategy established by most large organizations to promote efficient and safe use of data across the networks within their organizations
• Storage area network (SAN)


  Architecture to link remote computer storage devices, user's computer provides file system, SAN provides disk space
• Disaster recovery specialists are responsible for recovering systems and data after a disaster strokes
• General employer requirements for disaster recovery specialists include bachelor's or associate's degree in computer science or information systems, experience in the field and skills in networking, security and DBA, communication and skills and be able to handle high-stress situations
• Annual salary of disaster recovery specialists is $73 K to $92 K
• In the future, photos and videos may be stored using heat, lasers, or even DNA, and both magnetic disk manufacturers and flash memory researchers are working on increasing storage without increasing physical size