Are networks now faster than disks?

Here are some numbers that you are probably looking for, as quoted by Jeff Dean, a Google Fellow:

Numbers Everyone Should Know

L1 cache reference                             0.5 ns
Branch mispredict                              5 ns
L2 cache reference                             7 ns
Mutex lock/unlock                            100 ns (25)
Main memory reference                        100 ns
Compress 1K bytes with Zippy              10,000 ns (3,000)
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 network   10,000,000 ns
Read 1 MB sequentially from disk      30,000,000 ns (20,000,000)
Send packet CA->Netherlands->CA      150,000,000 ns

It’s from his presentation titled Designs, Lessons and Advice from Building Large Distributed Systems and you can get it here:

• Dr Jeff Dean Keynote PDF or on slideshare.net

The talk was given at Large-Scale Distributed Systems and Middleware (LADIS) 2009.

Other Info

• Google Pro Tip: Use Back-Of-The-Envelope-Calculations To Choose The Best Design
• Stanford 295 Talk Software Engineering Advice from Building Large-Scale Distributed Systems

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It’s said that gcc -O4 emails your code to Jeff Dean for a rewrite.

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