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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-6981) DN upgrade with layout version change should not use trash
Date Mon, 01 Sep 2014 21:41:20 GMT
Arpit Agarwal created HDFS-6981:
-----------------------------------

             Summary: DN upgrade with layout version change should not use trash
                 Key: HDFS-6981
                 URL: https://issues.apache.org/jira/browse/HDFS-6981
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: datanode
    Affects Versions: 3.0.0
            Reporter: James Thomas


Post HDFS-6800, we can encounter the following scenario:
# We start with DN software version -55 and initiate a rolling upgrade to version -56
# We delete some blocks, and they are moved to trash
# We roll back to DN software version -55 using the -rollback flag – since we are running
the old code (prior to this patch), we will restore the previous directory but will not delete
the trash
# We append to some of the blocks that were deleted in step 2
# We then restart a DN that contains blocks that were appended to – since the trash still
exists, it will be restored at this point, the appended-to blocks will be overwritten, and
we will lose the appended data

So I think we need to avoid writing anything to the trash directory if we have a previous
directory.

Thanks to [~james.thomas] for reporting this.



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