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From Qing Yan <qing...@gmail.com>
Subject ZAB kick Paxos butt?
Date Wed, 20 Jan 2010 10:16:25 GMT
    Anyone familer with Paxos protocol here?
    I was doing some comparision of ZAB vs Paxos... first of all, ZAB's FIFO
based protocol is really cool!

 http://wiki.apache.org/hadoop/ZooKeeper/PaxosRun mentioned the
inconsistency case for Paxos("the state change B depends upon A, but A was
not committed").
 In the "Paxos made simple" paper, author suggests fill the GAP (lost state
machine changes) with "NO OP" opeartion.

  Now I have some serious doubts how could Paxos be any useful in the real
world. yeah you do reach the consesus - albeit the content
is inconsistent/corrupted !?

  E.g. on the wiki page, why the Paxos state machine allow fire off 27,28
concurrently where there is actually depedency? Shouldn't you wait instance
27 to be committed before start 28?
  Did I miss something?

  Thanks for the enlight!



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