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https://issues.apache.org/jira/browse/HBASE-6233?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13409212#comment-13409212
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Matteo Bertozzi commented on HBASE-6233:
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{quote}
We have to move it? We can't just decrement references? We'd have to undo the
association of files with particular regions – the layout under HBASE.ROOTDIR
would not be as it is now. We'd present a logical view that was detached from
how the hfiles were stored in hdfs.
{quote}
+1 on this. If we're going to change the HBASE.ROOTDIR layout everything will
be much easier. Since we just need a "flat" folder that contains all the hfiles
and each table can keep track of its own file by scanning .META. in this way we
can really use the ref-count and we don't have to move the files around.
But again, this require code changes and changes in how the data is stored
(What are the policy for compatibility?).
Also while fixing .META. problems with hbck is useful to look inside the the
/hbase/<table> directory to see which files are present in a particoular table.
> [brainstorm] snapshots: hardlink alternatives
> ---------------------------------------------
>
> Key: HBASE-6233
> URL: https://issues.apache.org/jira/browse/HBASE-6233
> Project: HBase
> Issue Type: Brainstorming
> Reporter: Matteo Bertozzi
> Assignee: Matteo Bertozzi
> Attachments: Restore-Snapshot-Hardlink-alternatives.pdf
>
>
> Discussion ticket around snapshots and hardlink alternatives.
> (See the HDFS-3370 discussion about hardlink and implementation problems)
> (taking for a moment WAL out of the discussion and focusing on hfiles)
> With hardlinks available taking snapshot will be fairly easy:
> * (hfiles are immutable)
> * hardlink to .snapshot/name to take snapshot
> * hardlink from .snapshot/name to restore the snapshot
> * No code change needed (on fs.delete() only one reference is deleted)
> but we don't have hardlinks, what are the alternatives?
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