Google Pro Tip: Use Back-of-the-envelope-calculations to Choose the Best Design - High Scalability -
http://highscalability.com/blog/2011/1/26/google-pro-tip-use-back-of-the-envelope-calculations-to-choo.html
Building software systems at Google
http://static.googleusercontent.com/external_content/untrusted_dlcp/research.google.com/en/us/people/jeff/Stanford-DL-Nov-2010.pdf
原文：http://www.cnblogs.com/pegasus923/p/5550801.html