The Memory Hierarchy

Main Memory Disk Tape

• Volatile

• limited address

spaces

• expensive

• average access

time:

10-100 nanoseconds

• 5-10 MB/S

transmission rates

• 2-10 GB 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

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