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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6469) Coordinated replication of the namespace using ConsensusNode
Date Tue, 15 Jul 2014 19:00:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14062502#comment-14062502
] 

Sanjay Radia commented on HDFS-6469:
------------------------------------

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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