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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9208) Disabling atime may fail clients like distCp
Date Thu, 08 Oct 2015 13:40:26 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14948658#comment-14948658
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Kihwal Lee commented on HDFS-9208:
----------------------------------

Really #3 is the only option. I was wrong about atime being 0. When {{INode}} is created,
the atime and mtime are set to identical value. option 1) and 2) are not possible.

> Disabling atime may fail clients like distCp
> --------------------------------------------
>
>                 Key: HDFS-9208
>                 URL: https://issues.apache.org/jira/browse/HDFS-9208
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Kihwal Lee
>            Assignee: Mingliang Liu
>
> When atime is disabled, {{setTimes()}} throws an exception if the passed-in atime is
not -1.  But since atime is not -1, distCp fails when it tries to set the mtime and atime.

> There are several options:
> 1) make distCp check for 0 atime and call {{setTimes()}} with -1. I am not very enthusiastic
about it.
> 2) make NN also accept 0 atime in addition to -1, when the atime support is disabled.
> 3) support setting mtime & atime regardless of the atime support.  The main reason
why atime is disabled is to avoid edit logging/syncing during {{getBlockLocations()}} read
calls. Explicit setting can be allowed.



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