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https://issues.apache.org/jira/browse/HDFS-3370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13396961#comment-13396961
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Jesse Yates commented on HDFS-3370:
-----------------------------------
Maybe I'm missing something here...
bq. Backup itself only becomes safe if HDFS (not HBase) promises to never
modify a file once it is closed. Otherwise, a process that accidentally writes
into the hard-linked file will corrupt "both" copies
At least for the HBase case, if we set the file permissions to be 744, you will
only have an hbase process that could mess up the file (which it won't do once
we close the file) and then an errant process can only slow down other reader
processes. That would make it sufficient at least for HBase backups, but
clearly not for general HDFS backups.
> 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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