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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5620) discp can preserve modification times of files
Date Tue, 26 May 2009 21:15:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713260#action_12713260

Tsz Wo (Nicholas), SZE commented on HADOOP-5620:

> Dhruba told me modification times of directories are not persistent, that is, on namenode
restart they are set to the latest modification time amongst the files they contain.
I just have checked the codes.  It seems not true.  

Also, DistCp works on general FileSystem.  It should not depend on a particular implementation.

> If we get atime inside the if, it will be the copy time (last access after copying the
file) instead of the latest access time before copying, which is what we need for migration.
FileStatus is a local object.  Once it has been obtained from a FileSystem it remains unchanged
even the actual status of the file is changed.  So the atime inside the if-statement will
be the latest access time before copying since getFileStatus is called before copying.

 BTW, there is a white space change in the patch, could you remove it?

> discp can preserve modification times of files
> ----------------------------------------------
>                 Key: HADOOP-5620
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5620
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: tools/distcp
>            Reporter: dhruba borthakur
>            Assignee: Rodrigo Schmidt
>             Fix For: 0.21.0
>         Attachments: HADOOP-5620.patch
> It will be helpful if distcp can preserve the modification time and access time of files.
This helps to archive/unarchive hdfs files.

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