Wenwu Peng created HDFS-6316:
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             Summary: Only one replica for each block in single-rack cluster
                 Key: HDFS-6316
                 URL: https://issues.apache.org/jira/browse/HDFS-6316
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 1.2.1
            Reporter: Wenwu Peng


In HDFS 1,only one replica for each block when in single rack cluster when 
enble nodegroup awareness. in my environment, there is single rack and four 
nodegroup
even though the replication=3.

Steps:
1. setup a hadoop cluster with all pyhsical in same rack
2. Run hadoop fs -copyFromLocal /data /test
3. Run hadoop fsck /test -files -locations -blocks -racks

Topology:
192.168.0.1   /default-rack/nodegroup1
192.168.0.2   /default-rack/odegroup1
192.168.0.3   /default-rack/nodegroup1
192.168.0.4   /default-rack/nodegroup2
192.168.0.5  /default-rack/nodegroup2
192.168.0.6  /default-rack/nodegroup2
192.168.0.7   /default-rack/nodegroup3
192.168.0.8   /default-rack/nodegroup3
192.168.0.9  /default-rack/nodegroup4
192.168.0.19   /default-rack/nodegroup4

Namenode.log
2014-01-14 00:51:19,884 WARN 
org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Not able to place enough 
replicas, still in need of 2 to reach 3
Not able to place enough replicas

Note: 
1. Not exist in Hadoop 2.2.0
2. Not exist when have more than one rack 




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