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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5724) Datanode should report deletion of blocks to Namenode explicitly
Date Mon, 11 May 2009 17:51:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708131#action_12708131
] 

Hairong Kuang commented on HADOOP-5724:
---------------------------------------

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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