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Algorithms are often designed with correctness, efficiency, and/or conciseness as the primary goals. Although these are all worthy goals, we believe that understandability is just as important. None of the other goals can be achieved until developers render the algorithm into a practical implementation, which will inevitably deviate from and expand upon the published form. Unless developers have a deep understanding of the algorithm and can create intuitions about it, it will be difficult for them to retain its desirable properties in their implementation.
In this paper we addressed the issue of distributed consensus, where a widely accepted but impenetrable algorithm, Paxos, has challenged students and developers for many years. We developed a new algorithm, Raft, which we have shown to be more understandable than Paxos. We also believe that Raft provides a better foundation for system building. Using understandability as the primary design goal changed the way we approached the design of Raft; as the design progressed we found ourselves reusing a few techniques repeatedly, such as decomposing the problem and simplifying the state space. These techniques not only improved the understandability of Raft but also made it easier to convince ourselves of its correctness.
The user study would not have been possible without the support of Ali Ghodsi, David Mazi`eres, and the students of CS 294-91 at Berkeley and CS 240 at Stanford. Scott Klemmer helped us design the user study, and Nelson Ray advised us on statistical analysis. The Paxos slides for the user study borrowed heavily from a slide deck originally created by Lorenzo Alvisi. Special thanks go to David Mazi`eres and Ezra Hoch for finding subtle bugs in Raft. Many people provided helpful feedback on the paper and user study materials, including Ed Bugnion, Michael Chan, Hugues Evrard, Daniel Giffin, Arjun Gopalan, Jon Howell, Vimalkumar Jeyakumar, Ankita Kejriwal, Aleksandar Kracun, Amit Levy, Joel Martin, Satoshi Matsushita, Oleg Pesok, David Ramos, Robbert van Renesse, Mendel Rosenblum, Nicolas Schiper, Deian Stefan, Andrew Stone, Ryan Stutsman, David Terei, Stephen Yang, Matei Zaharia, 24 anonymous conference reviewers (with duplicates), and especially our shepherd Eddie Kohler. Werner Vogels tweeted a link to an earlier draft, which gave Raft significant exposure. This work was supported by the Gigascale Systems Research Center and the Multiscale Systems Center, two of six research centers funded under the Focus Center Research Program, a Semiconductor Research Corporation program, by STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA, by the National Science Foundation under Grant No. 0963859, and by grants from Facebook, Google, Mellanox, NEC, NetApp, SAP, and Samsung. Diego Ongaro is supported by The Junglee Corporation Stanford Graduate Fellowship.
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原文地址：http://my.oschina.net/daidetian/blog/490994
