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https://issues.apache.org/jira/browse/HDFS-2576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642189#comment-13642189
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Tsz Wo (Nicholas), SZE commented on HDFS-2576:
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- In BlockPlacementPolicyDefault, it should use the oldExcludedNodes when
choosing the remaining nodes. Also, what should happen if a node is in both
favoredNodes and excludedNodes?
- In BlockPlacementPolicy and BlockPlacementPolicyDefault, use
Collections.<DatanodeDescriptor>emptyList() instead of new
ArrayList<DatanodeDescriptor>().
- Change void resolveNetworkLocation(DatanodeDescriptor) to String
resolveNetworkLocation(DatanodeID). Then, we only need to create DatanodeID
but not DatanodeDescriptor in the new resolveNetworkLocation(String) method.
- Move getDatanodeDescriptor(String address) from BlockManager to
DatanodeManager.
> Namenode should have a favored nodes hint to enable clients to have control
> over block placement.
> -------------------------------------------------------------------------------------------------
>
> Key: HDFS-2576
> URL: https://issues.apache.org/jira/browse/HDFS-2576
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Pritam Damania
> Assignee: Devaraj Das
> Fix For: 2.0.5-beta
>
> Attachments: hdfs-2576-1.txt, hdfs-2576-trunk-1.patch,
> hdfs-2576-trunk-2.patch, hdfs-2576-trunk-7.1.patch, hdfs-2576-trunk-7.patch,
> hdfs-2576-trunk-8.1.patch, hdfs-2576-trunk-8.patch
>
>
> Sometimes Clients like HBase are required to dynamically compute the
> datanodes it wishes to place the blocks for a file for higher level of
> locality. For this purpose there is a need of a way to give the Namenode a
> hint in terms of a favoredNodes parameter about the locations where the
> client wants to put each block. The proposed solution is a favored nodes
> parameter in the addBlock() method and in the create() file method to enable
> the clients to give the hints to the NameNode about the locations of each
> replica of the block. Note that this would be just a hint and finally the
> NameNode would look at disk usage, datanode load etc. and decide whether it
> can respect the hints or not.
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