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From "Frode Halvorsen (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7787) Wrong priorty of replication
Date Thu, 12 Feb 2015 13:24:11 GMT
Frode Halvorsen created HDFS-7787:

             Summary: Wrong priorty of replication
                 Key: HDFS-7787
                 URL: https://issues.apache.org/jira/browse/HDFS-7787
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: datanode
    Affects Versions: 2.6.0
         Environment: 2 namenodes HA, 6 datanodes in two racks
            Reporter: Frode Halvorsen

Each file has a setting of 3 replicas. split on different racks.
After a simulated crash of one rack (shutdown of all nodes, deleted data-directory an started
nodes) and decommssion of one of the nodes in the orther rack the replication does not follow
'normal' rules...

My cluster has appx 25 mill files, and the one node I now try to decommision has 9 millions
underreplicated blocks, and 3,5 million blocks with 'no live replicas'. After a restart of
the node, it starts to replicate both types of blocks, but after a while, it only repliates
under-replicated blocks with other live copies. I would think that the 'normal' way to do
this would be to make sure that all blocks this node keeps the only copy of, should be the
first to be replicated/balanced ?  Another thing, is that this takes 'forever'. The rate it's
going now it will run for a couple of months before I can take down the node for maintance..
It only has appx 250 G of data in total .. 

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