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Date: Fri, 22 Aug 2008 05:34:50 -0700 (PDT)
From: "Hudson (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-3328) DFS write pipeline : only the last
 datanode needs to verify checksum
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    [ https://issues.apache.org/jira/browse/HADOOP-3328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624729#action_12624729 ] 

Hudson commented on HADOOP-3328:
--------------------------------

Integrated in Hadoop-trunk #581 (See [http://hudson.zones.apache.org/hudson/job/Hadoop-trunk/581/])

> DFS write pipeline : only the last datanode needs to verify checksum
> --------------------------------------------------------------------
>
>                 Key: HADOOP-3328
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3328
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.16.0
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.19.0
>
>         Attachments: HADOOP-3328.patch, HADOOP-3328.patch
>
>
> Currently all the datanodes in DFS write pipeline verify checksum. Since the current protocol includes acks from  the datanodes, an ack from the last node could also serve as verification that checksum ok. In that sense, only the last datanode needs to verify checksum. Based on [this comment|http://issues.apache.org/jira/browse/HADOOP-1702?focusedCommentId=12575553#action_12575553] from HADOOP-1702, CPU consumption might go down by another 25-30% (4/14) after HADOOP-1702. 
> Also this would make it easier to use transferTo() and transferFrom() on intermediate datanodes since they don't need to look at the data.

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