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Date: Tue, 12 May 2009 11:50:45 -0700 (PDT)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-5724) Datanode should report deletion of
 blocks to Namenode explicitly
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    [ https://issues.apache.org/jira/browse/HADOOP-5724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708561#action_12708561 ] 

Raghu Angadi commented on HADOOP-5724:
--------------------------------------

>>    I don't think so... the blocks are removed from the datanode list only after the blockreport. from what I can see, could be mistaken.
> Block is indeed deleted from the blocksMap when the file is deleted. 

A simple test on trunk shows otherwise. On a clean cluster with one datanode: 

# create a file 
# Check that http://namenode:50070/dfsnodelist.jsp?whatNodes=LIVE shows one block 
# Delete the file
# Check the datanode list page again. The block is still counted.
# You will see that count goes to zero only after a block report from the datanode.

> 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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