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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-395) DFS Scalability: Incremental block reports
Date Fri, 26 Aug 2011 04:26:29 GMT

    [ https://issues.apache.org/jira/browse/HDFS-395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13091567#comment-13091567
] 

Hudson commented on HDFS-395:
-----------------------------

Integrated in Hadoop-Hdfs-trunk-Commit #870 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk-Commit/870/])
    Move change log for HDFS-395 from 0.23 section to trunk

hairong : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1161987
Files : 
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt


> DFS Scalability: Incremental block reports
> ------------------------------------------
>
>                 Key: HDFS-395
>                 URL: https://issues.apache.org/jira/browse/HDFS-395
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: data-node, name-node
>            Reporter: dhruba borthakur
>            Assignee: Tomasz Nykiel
>             Fix For: 0.24.0
>
>         Attachments: blockReportPeriod.patch, explicitAcks.patch-3, explicitAcks.patch-4,
explicitAcks.patch-5, explicitAcks.patch-6, explicitDeleteAcks.patch
>
>
> I have a cluster that has 1800 datanodes. Each datanode has around 50000 blocks and sends
a block report to the namenode once every hour. This means that the namenode processes a block
report once every 2 seconds. Each block report contains all blocks that the datanode currently
hosts. This makes the namenode compare a huge number of blocks that practically remains the
same between two consecutive reports. This wastes CPU on the namenode.
> The problem becomes worse when the number of datanodes increases.
> One proposal is to make succeeding block reports (after a successful send of a full block
report) be incremental. This will make the namenode process only those blocks that were added/deleted
in the last period.

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