io存取速度

Google的Jeff Dean給的一些數據(一個talk的ppt, "Designs, Lessons and Advice from Building Large Distributed Systems" 23頁)，可以看到1Gbps的網絡比硬盤的bandwidth高了很多，記住這些數據對設計高性能系統和對系統的性能估算很有幫助。

L1 cache reference 0.5 ns

Branch mispredict 5 ns

L2 cache reference 7 ns

Mutex lock/unlock 25 ns

Main memory reference 100 ns

Compress 1K bytes with Zippy 3,000 ns

Send 2K bytes over 1 Gbps network 20,000 ns

Read 1 MB sequentially from memory 250,000 ns

Round trip within same datacenter 500,000 ns

Disk seek 10,000,000 ns

Read 1 MB sequentially from disk 20,000,000 ns

Send packet CA->Netherlands->CA 150,000,000 ns