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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-8461) Erasure coding: fix priority level of UnderReplicatedBlocks for striped block
Date Fri, 22 May 2015 06:40:17 GMT
Walter Su created HDFS-8461:
-------------------------------

             Summary: Erasure coding: fix priority level of UnderReplicatedBlocks for striped
block
                 Key: HDFS-8461
                 URL: https://issues.apache.org/jira/browse/HDFS-8461
             Project: Hadoop HDFS
          Issue Type: Sub-task
            Reporter: Walter Su
            Assignee: Walter Su


{code:title=UnderReplicatedBlocks.java}
  private int getPriority(int curReplicas,
  ...
    } else if (curReplicas == 1) {
      //only on replica -risk of loss
      // highest priority
      return QUEUE_HIGHEST_PRIORITY;
  ...
{code}
For stripe blocks, we should return QUEUE_HIGHEST_PRIORITY when curReplicas == 6( Suppose
6+3 schema).

That's important. Because
{code:title=BlockManager.java}
DatanodeDescriptor[] chooseSourceDatanodes(BlockInfo block,
  ...
     if(priority != UnderReplicatedBlocks.QUEUE_HIGHEST_PRIORITY 
          && !node.isDecommissionInProgress() 
          && node.getNumberOfBlocksToBeReplicated() >= maxReplicationStreams)
      {
        continue; // already reached replication limit
      }
  ...
{code}
It may return not enough source DNs ( maybe 5), and failed to recover.



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