Disk Access

• Access time =

  queue + seek + rotational + transfer + overhead
  

• Seek time

  • move arm over track
  • average is confusing (startup, slowdown, locality of accesses)

• Rotational latency

  • wait for sector to rotate under head
  • average = 0.5/(3600 RPM) = 8.3ms

• Transfer Time

  • f(size, BW bytes/sec)

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