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