io存取速度


Google的Jeff Dean给的一些数据(一个talk的ppt, "Designs, Lessons and Advice from Building Large Distributed Systems" 23页),可以看到1Gbps的网络比硬盘的bandwidth高了很多,记住这些数据对设计高性能系统和对系统的性能估算很有帮助。

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

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