Thanks for this paper info... It is formalized and not easy to understand.
Still reading... :P -- daidong Sent with Sparrow On 2011年4月21日星期四 at 上午7:21, André Oriani [via zookeeper-user] wrote: > If you wanna go deep on Zab http://research.yahoo.com/files/YL-2010-007.pdf > > - > André > > On Wed, Apr 20, 2011 at 17:26, Benjamin Reed <[hidden email]> wrote: > > > just to add a bit to alex's reponse: we do a simplified 2pc since we > > do not have aborts. we also differ from 2pc during recovery which is > > made up of two sub phases. > > > > ben > > > > On Wed, Apr 20, 2011 at 11:29 AM, Alexander Shraer > > <[hidden email]> wrote: > >> Hi, > >> > >> Regarding your first question - ZAB has two parts - the broadcast protocol > >> you mention, > >> which is executed by a leader, and the leader election protocol, which > >> recovers from a leader failure. > >> This is similar to the way other state-machine replication algorithms > >> work, where you have > >> a fast normal mode and a slower recovery mode (you don't need to execute > >> both all the time - only when the leader fails). > >> See Paxos state-machine replication for example (section 3): > >> http://research.microsoft.com/en-us/um/people/lamport/pubs/pubs.html#paxos-simple > >> > >> Regarding your second question - Zookeeper basically guarantees so called > >> "sequential consistency" semantics. > >> This guarantees that the real execution looks to clients like some > >> sequential execution in which > >> the operations of every client appear in the order they were submitted. It > >> does not guarantee that a read of one client > >> returns the latest value written by another client. This allows reads to > >> be executed locally. If you need to return the latest > >> state, you can use the sync() call which flushes the pending updates > >> between the leader and a follower. > >> See also the "consistency guarantees" section here: > >> http://hadoop.apache.org/zookeeper/docs/r3.3.1/zookeeperProgrammers.html > >> > >> Alex > >> > >>> -----Original Message----- > >>> From: daidong [mailto:[hidden email]] > >>> Sent: Wednesday, April 20, 2011 2:38 AM > >>> To: [hidden email] > >>> Subject: Problems about Zab protocol > >>> > >>> Hi, everyone. > >>> > >>> Recently, i read the paper "a simple total ordered broadcast protocol" > >>> and > >>> there are some problems i can not figure out. Hope anyone can help > >>> me... :P > >>> > >>> The paper describes the Zab protocol as a 2 phase commit protocol when > >>> system is under broadcast mode. However some paper(Skeen 82, "A Quorum > >>> Based > >>> Commit Protocol") has mentioned if we want to extend an 2PC to adapt a > >>> quorum based commit protocol we must introduce a three phase commit > >>> protocol(In fact, i haven't quit understood this, :( ). However > >>> according > >>> Zab paper, this still can be done. Why and how to do this? > >>> > >>> Secondly, even Zookeeper can guarantee that status in different > >>> followers > >>> are consistent. However, this consistency only works among a quorum of > >>> followers that has acked the COMMIT. As the client can connect to any > >>> followers when perform reading action, so what happens if the client > >>> happens > >>> to connect with the follower that has not acked the COMMIT? I can not > >>> find > >>> the information in this paper... > >>> > >>> If i ask some naive question, Hope anybody can tell me where i can find > >>> the > >>> answer or some suggestions, thanks :) > >>> > >>> > >>> -- > >>> View this message in context: http://zookeeper- > >>> user.578899.n2.nabble.com/Problems-about-Zab-protocol- > >>> tp6290102p6290102.html > >>> Sent from the zookeeper-user mailing list archive at Nabble.com. > >> > > > > > If you reply to this email, your message will be added to the discussion > below: > http://zookeeper-user.578899.n2.nabble.com/Problems-about-Zab-protocol-tp6290102p6292678.html > > To unsubscribe from Problems about Zab protocol, click here. > > > -- View this message in context: http://zookeeper-user.578899.n2.nabble.com/Problems-about-Zab-protocol-tp6290102p6293373.html Sent from the zookeeper-user mailing list archive at Nabble.com.
