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https://issues.apache.org/jira/browse/HDFS-2202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13072862#comment-13072862
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Eric Payne commented on HDFS-2202:
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[exec] +1 overall.
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[exec] +1 @author. The patch does not contain any @author tags.
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[exec] +1 tests included. The patch appears to include 3 new or
modified tests.
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[exec] +1 javadoc. The javadoc tool did not generate any warning
messages.
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of javac compiler warnings.
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(version 1.3.9) warnings.
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[exec] +1 release audit. The applied patch does not increase the
total number of release audit warnings.
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[exec] +1 system test framework. The patch passed system test
framework compile.
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BUILD SUCCESSFUL
> Changes to balancer bandwidth should not require datanode restart.
> ------------------------------------------------------------------
>
> Key: HDFS-2202
> URL: https://issues.apache.org/jira/browse/HDFS-2202
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: balancer, data-node
> Affects Versions: 0.20.205.0, 0.23.0
> Reporter: Eric Payne
> Assignee: Eric Payne
> Fix For: 0.20.205.0, 0.23.0
>
> Attachments: HDFS-2171.patch, HDFS-2202.0.20.205.0.v1.patch,
> HDFS-2202.0.20.205.0.v2.patch, HDFS-2202.0.23.0.v1.patch,
> HDFS-2202.0.23.0.v2.patch, HDFS-2202.patch
>
>
> Currently in order to change the value of the balancer bandwidth
> (dfs.datanode.balance.bandwidthPerSec), the datanode daemon must be restarted.
> The optimal value of the bandwidthPerSec parameter is not always (almost
> never) known at the time of cluster startup, but only once a new node is
> placed in the cluster and balancing is begun. If the balancing is taking too
> long (bandwidthPerSec is too low) or the balancing is taking up too much
> bandwidth (bandwidthPerSec is too high), the cluster must go into a
> "maintenance window" where it is unusable while all of the datanodes are
> bounced. In large clusters of thousands of nodes, this can be a real
> maintenance problem because these "mainenance windows" can take a long time
> and there may have to be several of them while the bandwidthPerSec is
> experimented with and tuned.
> A possible solution to this problem would be to add a -bandwidth parameter to
> the balancer tool. If bandwidth is supplied, pass the value to the datanodes
> via the OP_REPLACE_BLOCK and OP_COPY_BLOCK DataTransferProtocol requests.
> This would make it necessary, however, to change the DataTransferProtocol
> version.
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