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From "Yi Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6871) Improve NameNode performance when creating file
Date Thu, 21 Aug 2014 01:43:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14104929#comment-14104929
] 

Yi Liu commented on HDFS-6871:
------------------------------

Besides using one single editlog record for creating file + overwrite, we still need to remove
the blocks after the logSync.

> Improve NameNode performance when creating file  
> -------------------------------------------------
>
>                 Key: HDFS-6871
>                 URL: https://issues.apache.org/jira/browse/HDFS-6871
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode, performance
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>            Priority: Critical
>             Fix For: 2.6.0
>
>         Attachments: HDFS-6871.001.patch, HDFS-6871.002.patch, HDFS-6871.003.patch
>
>
> Creating file with overwrite flag will cause NN fall into flush edit logs and block other
requests if the file exists.
> When we create a file with overwrite flag (default is true) in HDFS, NN will remove original
file if it exists. In FSNamesystem#startFileInternal, NN already holds the write lock, it
calls {{deleteInt}} if the file exists, there is logSync in {{deleteInt}}. So in this case,
logSync is under write lock, it will heavily affect the NN performance. 
> We should ignore the force logSync in {{deleteInt}} in this case.



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