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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-202) Log Aggregation generates a storm of fsync() for namenode
Date Tue, 06 Nov 2012 18:56:12 GMT

    [ https://issues.apache.org/jira/browse/YARN-202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13491709#comment-13491709
] 

Hudson commented on YARN-202:
-----------------------------

Integrated in Hadoop-trunk-Commit #2962 (See [https://builds.apache.org/job/Hadoop-trunk-Commit/2962/])
    YARN-202. Log Aggregation generates a storm of fsync() for namenode (Kihwal Lee via bobby)
(Revision 1406269)

     Result = SUCCESS
bobby : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1406269
Files : 
* /hadoop/common/trunk/hadoop-yarn-project/CHANGES.txt
* /hadoop/common/trunk/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/logaggregation/AggregatedLogFormat.java

                
> Log Aggregation generates a storm of fsync() for namenode
> ---------------------------------------------------------
>
>                 Key: YARN-202
>                 URL: https://issues.apache.org/jira/browse/YARN-202
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.0.2-alpha, 0.23.4
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>            Priority: Critical
>             Fix For: 3.0.0, 2.0.3-alpha, 0.23.5
>
>         Attachments: yarn-202.patch
>
>
> When the log aggregation is on, write to each aggregated container log causes hflush()
to be called. For large clusters, this can creates a lot of fsync() calls for namenode. 
> We have seen 6-7x increase in the average number of fsync operations compared to 1.0.x
on a large busy cluster. Over 99% of fsync ops were for log aggregation writing to tmp files.

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