[jira] [Created] (HBASE-18693) adding an option to restore_snapshot to move mob files from archive dir to working dir

["huaxiang sun (JIRA)" <ji...@apache.org>]

huaxiang sun created HBASE-18693:
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             Summary: 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


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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