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https://issues.apache.org/jira/browse/HDFS-3370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13402735#comment-13402735
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Daryn Sharp commented on HDFS-3370:
-----------------------------------
Nice idea, but I think it gets much more complicated. Retaining ref-counted
paths after deletion in the origin namespace requires an "inode id". A new api
to reference paths based on the id is required. We aren't so soft anymore...
The inode id needs to be secured since it bypasses all parent dir permissions,
yet the id should be identical for all links in order for copy utils to
distinguish identical inodes.
Now comes the worst part: the client. Will the NNs proxy fs stream operations
to each other with a secure api for referencing inode ids? Or will they
redirect the client to the origin NN? If they redirect, how to protect against
the client guessing ids, or saving them for later replay even when the dir
privs prevent access?
> 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-HardLink.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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