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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-432) support undelete, snapshots, or other mechanism to recover lost files
Date Thu, 01 Feb 2007 23:35:06 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12469617
] 

Doug Cutting commented on HADOOP-432:
-------------------------------------

> expunge(), as implemented, purges the entire trash

No, it only removes things in folders older than the interval.  So, in particular, it never
removes the current trash, and won't remove a checkpoint until its older than the interval.

> results in a large load on the namenode

Expunge lists checkpoints, then removes entire checkpoints with a single call to the namenode.
 So it could take a long time on the namenode if the checkpoint has lots of files, but it
doesn't make a lot of calls to the namenode: all directory enumeration except of the top-level
checkpoints is done server-side, at the namenode.  So the RPC load on the namenode is minimized.

> It would be nice if the code, when deleting a file, checked if the source file is already
in the trash and would expunge it

Yes, that would be a useful feature.  Calling moveToTrash() on any path that begins with the
trash's root should cause it to be immediately removed.  +1


> support undelete, snapshots, or other mechanism to recover lost files
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-432
>                 URL: https://issues.apache.org/jira/browse/HADOOP-432
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Yoram Arnon
>         Assigned To: Doug Cutting
>         Attachments: trash.patch, undelete12.patch, undelete16.patch, undelete17.patch
>
>
> currently, once you delete a file it's gone forever.
> most file systems allow some form of recovery of deleted files.
> a simple solution would be an 'undelete' command.
> a more comprehensive solution would include snapshots, manual and automatic, with scheduling
options.

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