I/O Latency in Relative Terms

 I/O Latency in Relative Terms

If Rotational disk I/O were one to twelve months, a CPU Cycle would be one second.



Event

Latency

Scaled

1 CPU Cycle

0.3 ns

1 second

Level 1 cache access

0.9 ns

3 second

Level 2 cache access

2.8 ns

9 seconds

Level 3 Cache access

12.9 ns

43 seconds

Main memory access (DRAM, from CPU)

120 ns

6  min

Solid-state disk I/O (flash memory)

50-150 µs

2-6 days

Rotational disk I/O

1-10 ms

1-12 months

Internet: San Francisco to New York

40 ms

4 years

Internet: San Francisco to UK

81 ms

8 years

Internet: San Francisco to Australia

183 ms

19 years

TCP packet retransmit

1-3 s

105-317 years


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