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https://issues.apache.org/jira/browse/HBASE-18693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16311744#comment-16311744
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huaxiang sun commented on HBASE-18693:
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Hi [~jingcheng.du], just want to follow up the review status, thanks.
> adding an option to restore_snapshot to move mob files from archive dir to
> working dir
> --------------------------------------------------------------------------------------
>
> Key: HBASE-18693
> URL: https://issues.apache.org/jira/browse/HBASE-18693
> Project: HBase
> Issue Type: Improvement
> Components: mob
> Affects Versions: 2.0.0-alpha-2
> Reporter: huaxiang sun
> Assignee: huaxiang sun
> Attachments: HBASE-18693.master.001.patch,
> HBASE-18693.master.002.patch, HBASE-18693.master.003.patch
>
>
> Today, there is a single mob region where mob files for all user regions are
> saved. There could be many files (one million) in a single mob directory.
> When one mob table is restored or cloned from snapshot, links are created for
> these mob files. This creates a scaling issue for mob compaction. In mob
> compaction's select() logic, for each hFileLink, it needs to call NN's
> getFileStatus() to get the size of the linked hfile. Assume that one such
> call takes 20ms, 20ms * 1000000 = 6 hours.
> To avoid this overhead, we want to add an option so that restore_snapshot can
> move mob files from archive dir to working dir. clone_snapshot is more
> complicated as it can clone a snapshot to a different table so moving that
> can destroy the snapshot. No option will be added for clone_snapshot.
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