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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3370) HDFS hardlink
Date Fri, 04 May 2012 20:06:49 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13268671#comment-13268671
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Sanjay Radia commented on HDFS-3370:
------------------------------------

The main advantage over symbolic links being that when the original link is deleted the 2nd
one keeps the actual data from being deleted. Correct?
Does the hard link  stay on the NN or does it propagate to the actual blocks on the DN?
I believe it is not necessary to propagate the link to the DNs based on the use cases you
have described.
                
> HDFS hardlink
> -------------
>
>                 Key: HDFS-3370
>                 URL: https://issues.apache.org/jira/browse/HDFS-3370
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Hairong Kuang
>            Assignee: Liyin Tang
>         Attachments: HDFS-HardLinks.pdf
>
>
> We'd like to add a new feature hardlink to HDFS that allows harlinked files to share
data without copying. Currently we will support hardlinking only closed files, but it could
be extended to unclosed files as well.
> Among many potential use cases of the feature, the following two are primarily used in
facebook:
> 1. This provides a lightweight way for applications like hbase to create a snapshot;
> 2. This also allows an application like Hive to move a table to a different directory
without breaking current running hive queries.

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