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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3799) Design a pluggable interface to place replicas of blocks in HDFS
Date Tue, 12 May 2009 14:09:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708447#action_12708447
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dhruba borthakur commented on HADOOP-3799:
------------------------------------------

> Replication policies may have other requirements other than number of racks,

Of course, this is true. But this depends on what type of replication policy one can come
up with and I would like to leave this for a future time. "co-location" of blocks would typically
be based on their pathnames, and the balancer could be extended to invoke the same BlockPlacement
policy interface to adhere to the policy.

However, in this patch, I would like to expose the name of the file via the BlockPlacement
policy interface. Any ideas here?

> 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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