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https://issues.apache.org/jira/browse/HDFS-6469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14062502#comment-14062502
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Sanjay Radia commented on HDFS-6469:
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bq. 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.
Konstantine, HDFS has supported parallel journals (ie multiple editlogs for a
long time.) that are written in parallel. A customer can use just QJM (which
gives at least 3 replicas) and can optionally have a local parallel editlog if
they want additional redundancy. What you are proposing is dual *serial*
journals.
> 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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