### Latency numbers from Systems Performance book                       Scaled
    CPU cycle .................................... 0.3 ns                 1 s
    L1 cache reference ........................... 0.9 ns                 3 s
    L2 cache reference ........................... 2.8 ns                 9 s
    L3 cache reference .......................... 12.9 ns                43 s
    Main memory access (DRAM, from CPU) .......... 120 ns                 6 min
    SSD 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 United Kingdom .... 81 ms                 8 years
    Internet : San Francisco to Australia ........ 183 ms                19 years
    TCP packet retransmit ........................ 1-3 s            105-317 years
    OS virtualization system reboot ................ 4 s                423 years
    SCSI command time-out ......................... 30 s                  3 millennia
    Hardware virtualization system reboot ......... 40 s                  4 millennia
    Physical system reboot ......................... 5 min               32 millennia

Assuming 3.3GHz CPU, ~1GB/sec SSD

Data by [Brendan Gregg | Systems Performance book](http://www.amazon.com/Systems-Performance-Enterprise-Brendan-Gregg/dp/0133390098)
via [@rzezeski](https://twitter.com/rzezeski/status/398306728263315456/photo/1)