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https://issues.apache.org/jira/browse/HDFS-6469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14054545#comment-14054545
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Konstantin Shvachko commented on HDFS-6469:
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Sanjay, by "not increasing journaling" I meant that if you use QJM then every
update on the NameNode results in writing into two journals: first into edits
log and then into QJM journal. The same as with ConsensusNode.The only
difference is that CNode first writes into CoordinationEngine journal then into
edits log.
HBase WAL triggers an HDFS edits log entry in two cases: when the WAL crosses
the block boundary and when it calls hflush(). The latter is called on each
write operation to HBase, so one can assume (modular WAL batching) that every
put in HBase results in an HDFS edits entry.
> 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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