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From "huaxiang sun (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-18693) adding an option to restore_snapshot to move mob files from archive dir to working dir
Date Fri, 25 Aug 2017 23:21:00 GMT
huaxiang sun created HBASE-18693:
------------------------------------

             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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