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https://issues.apache.org/jira/browse/HADOOP-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709021#action_12709021
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Konstantin Shvachko commented on HADOOP-3799:
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> The plugin wil analyze a set of past access patterns (stored in an external
> db)
What external db? Dhruba, could you please elaborate what you are trying to do.
May be in a form of some document.
Mixing different placement policies in the same (instance of) file system is
not a good idea imo. The policies may contradict each other.
I would rather allow to format a file system with a specific policy and then
keep it constant for the lifespan of the system.
This gives enough space for experimenting with different policies.
But I agree that the balancer and the fsck should be policy aware.
> 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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