The Memory Hierarchy
Main Memory                    Disk                               Tape
•Volatile
•limited address
 spaces
• expensive
• average access
   time:
  10-100 nanoseconds
•
• 5-10 MB/S
  transmission rates
• Gigs of storage
• average time to
  access a block:
  10-15 msecs.
• Need to consider
  seek, rotation,
  transfer times.
• Keep records “close”
   to each other.
• 1.5 MB/S transfer rate
• 280 GB typical
   capacity
• Only sequential access
• Not for operational
   data
Cache:
 access time 10 nano’s