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https://issues.apache.org/jira/browse/HDFS-6469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14111655#comment-14111655
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Sanjay Radia commented on HDFS-6469:
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My thoughts:
* I do believe that Paxos based NN would give faster failover than what NN HA
offers today (30sec to a few minutes but typically no more than 1 minute or
two). So this is clearly a benefit of CNode though I have not heard a single
customer complain about the failover time so far.
* The proposed solution does not increase the write throughput.
* The parallel reads advantage of CNode can be achieved in the current HA
setup with some work (this is discussed above). If this is the main benefit
than I rather pursue enhancing the NN standby to support reads. Further there
is existing on going work to improve the locking in the NN.
* I share Todd's view that ZK is not a usable "reference implementation" for
Paxos. One really needs a paxos library that can be plugged in rather than an
external server-based solution like ZK.
So at this stage I am having a hard time seeing the benefits to justify the
costs of adding this complexity. I do however understand the overhead that
Wandisco faces in integrating their solution with HDFS each time HDFS is
modified. Would a few plugin interfaces make it easier? I would be more than
happy to support adding such plugins if they would help.
> Coordinated replication of the namespace using ConsensusNode
> ------------------------------------------------------------
>
> Key: HDFS-6469
> URL: https://issues.apache.org/jira/browse/HDFS-6469
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Attachments: CNodeDesign.pdf
>
>
> This is a proposal to introduce ConsensusNode - an evolution of the NameNode,
> which enables replication of the namespace on multiple nodes of an HDFS
> cluster by means of a Coordination Engine.
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