Hadoop HDFS
  1. Hadoop HDFS
  2. HDFS-1940

Datanode can have more than one copy of same block when a failed disk is coming back in datanode

    Details

    • Type: Bug Bug
    • Status: Open
    • Priority: Major Major
    • Resolution: Unresolved
    • Affects Version/s: 0.20.204.0
    • Fix Version/s: None
    • Component/s: datanode
    • Labels:
      None

      Description

      There is a situation where one datanode can have more than one copy of same block due to a disk fails and comes back after sometime in a datanode. And these duplicate blocks are not getting deleted even after datanode and namenode restart.

      This situation can only happen in a corner case , when due to disk failure, the data block is replicated to other disk of the same datanode.

      To simulate this scenario I copied a datablock and the associated .meta file from one disk to another disk of same datanode, so the datanode is having 2 copy of same replica. Now I restarted datanode and namenode. Still the extra data block and meta file is not deleted from the datanode

      ls -l `find /grid/

      {0,1,2,3}

      /hadoop/var/hdfs/data/current -name blk_*`
      rw-rr- 1 hdfs users 7814 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376
      rw-rr- 1 hdfs users 71 May 13 21:05 /grid/1/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta
      rw-rr- 1 hdfs users 7814 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376
      rw-rr- 1 hdfs users 71 May 13 21:14 /grid/3/hadoop/var/hdfs/data/current/blk_1727421609840461376_579992.meta

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            People

            • Assignee:
              Bharath Mundlapudi
              Reporter:
              Rajit Saha
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              Dates

              • Created:
                Updated:

                Development