[jira] [Created] (HADOOP-14319) Under replicated blocks are not getting re-replicated

["Anil (JIRA)" <ji...@apache.org>]

Anil created HADOOP-14319:
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             Summary: Under replicated blocks are not getting re-replicated
                 Key: HADOOP-14319
                 URL: https://issues.apache.org/jira/browse/HADOOP-14319
             Project: Hadoop Common
          Issue Type: Bug
    Affects Versions: 2.7.2
            Reporter: Anil


Under replicated blocks are not getting re-replicated

In production Hadoop cluster of 5 Manangement + 5 Data Nodes, under replicated blocks are not re-replicated even after 2 days. 

Here is quick view of required configurations;

 Default replication factor:	3
 Average block replication:	3.0
 Corrupt blocks:		0
 Missing replicas:		0 (0.0 %)
 Number of data-nodes:		5
 Number of racks:		1

After bringing one of the DataNodes down, the replication factor for the blocks allocated on the Data Node became 2. It is observed that, even after 2 days the replication factor remains as 2. Under replicated blocks are not getting re-replicated to another DataNodes in the cluster. 

If a Data Node goes down, HDFS will try to replicate the blocks from Dead DN to other nodes and the priority. Are there any configuration changes to speed up the re-replication process for the under replicated blocks? 

When tested for blocks with replication factor 1, the re-replication happened to 2 overnight in around 10 hours of time. But blocks with 2 replication factor are not being re-replicated to default replication factor 3. 



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