Brahma Reddy Battula created HDFS-9127:
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             Summary: Re-replication for files with enough replicas in single 
rack
                 Key: HDFS-9127
                 URL: https://issues.apache.org/jira/browse/HDFS-9127
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Brahma Reddy Battula
            Assignee: Brahma Reddy Battula


Found while debugging testcases in HDFS-8647

 *Scenario:* 
=======

Start a cluster with Single rack with three DN's
write a file with RF=3
adde two Nodes with different racks

As per blockplacement policy ([Rack 
Awareness|http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/RackAwareness.html])
 atleast one replica needs to replicate to newly added rack.But it is not 
happening..Because of following reason.

{color:blue}
when cluster was single rack,block will be removed from {{neededReplications}} 
after 3 replicas.

later, after adding new rack, only replications will happen which are present 
in {{neededReplications}}

So for the blocks which already have enough replicas, new rack replications 
will not take place..
{color}



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