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https://issues.apache.org/jira/browse/HADOOP-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709027#action_12709027
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dhruba borthakur commented on HADOOP-3799:
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> What external db? Dhruba, could you please elaborate what you
We have deployed the scripts from HADOOP-3708 to collect (online) job logs
into a mysql DB. This DB also contains the hive query that the job makes. It is
easy to see what datasets are being used together in most queries. My idea is
to dynamically co-locate blocks based on these access patterns. I will present
those ideas in a separate JIRA (once this JIRA gets through)
> I would rather allow to format a file system with a specific policy and then
> keep it constant for the lifespan of the system.
That would be a fine goal for your cluster. However, I would like the API to be
more flexible than that. Does it sound reasonable?
> Design a pluggable interface to place replicas of blocks in HDFS
> ----------------------------------------------------------------
>
> Key: HADOOP-3799
> URL: https://issues.apache.org/jira/browse/HADOOP-3799
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: BlockPlacementPluggable.txt
>
>
> The current HDFS code typically places one replica on local rack, the second
> replica on remote random rack and the third replica on a random node of that
> remote rack. This algorithm is baked in the NameNode's code. It would be nice
> to make the block placement algorithm a pluggable interface. This will allow
> experimentation of different placement algorithms based on workloads,
> availability guarantees and failure models.
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