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https://issues.apache.org/jira/browse/HDFS-3077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447950#comment-13447950
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Suresh Srinivas commented on HDFS-3077:
---------------------------------------

Hey Todd, I have not looked at the work in this branch in a while. One thing I 
wanted to ask you about is, why are we using journal daemons to decide on an 
epoch? Could zookeeper be used for doing the same? What are the advantages of 
using journal daemons instead of zk? Adding this information to the document 
might also be useful.


                
> Quorum-based protocol for reading and writing edit logs
> -------------------------------------------------------
>
>                 Key: HDFS-3077
>                 URL: https://issues.apache.org/jira/browse/HDFS-3077
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: ha, name-node
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: QuorumJournalManager (HDFS-3077)
>
>         Attachments: hdfs-3077-partial.txt, hdfs-3077.txt, hdfs-3077.txt, 
> hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, hdfs-3077.txt, 
> qjournal-design.pdf, qjournal-design.pdf
>
>
> Currently, one of the weak points of the HA design is that it relies on 
> shared storage such as an NFS filer for the shared edit log. One alternative 
> that has been proposed is to depend on BookKeeper, a ZooKeeper subproject 
> which provides a highly available replicated edit log on commodity hardware. 
> This JIRA is to implement another alternative, based on a quorum commit 
> protocol, integrated more tightly in HDFS and with the requirements driven 
> only by HDFS's needs rather than more generic use cases. More details to 
> follow.

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