[
https://issues.apache.org/jira/browse/HDFS-3370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13293965#comment-13293965
]
Andy Isaacson commented on HDFS-3370:
-------------------------------------
{quote}
When users run "cp" in the linux file system against hard linked files, it will
copy the bytes, right?
{quote}
{{cp -a}} preserves hard links; {{cp -r}} breaks them (duplicates the bytes).
{quote}
I think we shall keep the same semantics here as well.
{quote}
I don't think it's a good idea to pretend that we can or should preserve
*every* corner case of the semantics of POSIX hard links. The Unix hard link
was originally a historical accident of the inode/dentry structure of the
filesystem, preserved because it's useful and has been heavily relied upon by
users of the Unix api. The implementation in something like ZFS or btrfs is
pretty far away from the original simplicity.
Since we don't have API compatibility with Unix and our underlying structure is
deeply different, it's a good idea to borrow the good ideas but take a
practical eye to where it makes sense to diverge.
> 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.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
