Mass-Storage Structure

• Management and ordering of disk access requests is important:
  • Huge speed gap between memory and disk.
  • Disk throughput is extremely sensitive to.
    • Request order $\Longrightarrow$ Disk Scheduling.
    • Placement of data on the disk $\Longrightarrow$ File System Design.
  • Disk scheduler must be aware of disk geometry.
• Disk management issues
  • Formatting
    • Physical: divide the blank slate into sectors identified by headers containing such information as sector number.
    • Logical: marking bad blocks; partitioning and writing a blank directory on disk; installing file allocation tables, and other relevant information (file system initialization).
  • Reliability
    • RAIDs (Redundant Array of Inexpensive Disks): various levels, level 0 is disk striping).