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https://issues.apache.org/jira/browse/HADOOP-5724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708131#action_12708131
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Hairong Kuang commented on HADOOP-5724:
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NN does not remove a replica from blocksMap immediately when scheduling to
delete the replica due to over-replication/corruption etc. The patch helps in
this case. But in case of block deletion due to file deletion etc., blocks are
removed from blocksMap immediately. For this kinds of blocks, this patch
introduces overhead. That's why we are holding off this patch now.
> Datanode should report deletion of blocks to Namenode explicitly
> ----------------------------------------------------------------
>
> Key: HADOOP-5724
> URL: https://issues.apache.org/jira/browse/HADOOP-5724
> Project: Hadoop Core
> Issue Type: Bug
> Reporter: Suresh Srinivas
> Assignee: Suresh Srinivas
> Fix For: 0.21.0
>
> Attachments: blockdel.patch, blockdel.patch
>
>
> Currently datanode notifies namenode newly added blocks and the blocks that
> are corrupt. There is no explicit message from the datanode to the namenode
> to indicate the deletion of blocks. Block reports from the datanode is the
> only way for the namenode to learn about the deletion of blocks at a
> datanode. With the addition of explicit request to indicate to block
> deletion, block report interval (which is currently 1 hour) can be increased
> to a longer duration. This reduces load on both namenode and datanodes.
>
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