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From "lohit vijayarenu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3328) DFS write pipeline : only the last datanode needs to verify checksum
Date Thu, 22 May 2008 21:55:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599205#action_12599205

lohit vijayarenu commented on HADOOP-3328:

The idea of verifying checksum only at last datanode is very good. +1

> 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
>         Attachments: 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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