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From "Uma Maheswara Rao G (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1765) Block Replication should respect under-replication block priority
Date Wed, 07 Dec 2011 16:46:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1765?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13164509#comment-13164509
] 

Uma Maheswara Rao G commented on HDFS-1765:
-------------------------------------------

I should have put the namesystem unlock in finally even though chooseUnderReplicatedBlocks
doesn't throw exception for more safe.
{code}
neededReplications.chooseUnderReplicatedBlocks(blocksToProcess);
+    namesystem.writeUnlock();
{code}


I will include this point in next patch along with the review comments if any.


Thanks
Uma
                
> Block Replication should respect under-replication block priority
> -----------------------------------------------------------------
>
>                 Key: HDFS-1765
>                 URL: https://issues.apache.org/jira/browse/HDFS-1765
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.23.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.24.0
>
>         Attachments: HDFS-1765.patch, HDFS-1765.patch, HDFS-1765.pdf, underReplicatedQueue.pdf
>
>
> Currently under-replicated blocks are assigned different priorities depending on how
many replicas a block has. However the replication monitor works on blocks in a round-robin
fashion. So the newly added high priority blocks won't get replicated until all low-priority
blocks are done. One example is that on decommissioning datanode WebUI we often observe that
"blocks with only decommissioning replicas" do not get scheduled to replicate before other
blocks, so risking data availability if the node is shutdown for repair before decommission
completes.

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