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From "Brahma Reddy Battula (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-9127) Re-replication for files with enough replicas in single rack
Date Wed, 23 Sep 2015 12:54:04 GMT
Brahma Reddy Battula created HDFS-9127:

             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


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.

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

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