Sunday, December 21, 2014

Storage Management

1. Storage Management
  • OS provides uniform, logical view of information storage
    • abstracts physical properties to logical storage unit (file)
    • each medium is controlled by device (i.e., disk drive, tape drive)
      • varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)
  • File system management
    • files usually organized into directories
    • access control on most file systems to determine who can access what
    • OS activities include
      • creating and deleting files and directories
      • primitives to manipulate files and dirs
      • mapping files onto secondary storage
      • backup files onto stable (non-volatile) storage media
2. Storage-Device Hierarchy



3. Caching
  • Important principle, performed at many levels in a computer (in hardware, operating system, software)
  • Information in use copied from slower to faster storage temporarily
  • Faster storage (cache) checked first to determine if information is there
    • if it is, information used directly from the cache (first)
    • if not, data copied to cache and used there
  • Cache smaller than storage being cached
    • cache management important design problem
    • cache size and replacement policy

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