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From "Koji Noguchi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3685) Unbalanced replication target
Date Wed, 02 Jul 2008 22:14:45 GMT
Unbalanced replication target 
------------------------------

                 Key: HADOOP-3685
                 URL: https://issues.apache.org/jira/browse/HADOOP-3685
             Project: Hadoop Core
          Issue Type: Bug
          Components: dfs
    Affects Versions: 0.17.0
            Reporter: Koji Noguchi
            Priority: Critical


In HADOOP-3633, namenode was assigning some datanodes to receive  hundreds of blocks in a
short period which caused datanodes to go out of memroy(threads).
Most of them were from remote rack.

Looking at the code, 

{noformat}
    166           chooseLocalRack(results.get(1), excludedNodes, blocksize,
    167                           maxNodesPerRack, results);
{noformat}

was sometimes not choosing the local rack of the writer(source).  

As a result, when a datanode goes down, other datanodes on the same rack were getting large
number of blocks from remote racks.


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