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https://issues.apache.org/jira/browse/HDFS-8818?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14644888#comment-14644888
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Chang Li commented on HDFS-8818:
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bq. Balancer waits until all block transfer are done each iteration and
Datanodes send a block receipt immediately once they receive a block.
But inside dispatchBlocks(), the Source will not wait for block gets
transferred, it will quickly iterate and ask namenode for more blocks, even
random offset can not prevent namenode from returning many same blocks, which
will be waste
> Allow Balancer to run faster
> ----------------------------
>
> Key: HDFS-8818
> URL: https://issues.apache.org/jira/browse/HDFS-8818
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: balancer & mover
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h8818_20150723.patch, h8818_20150727.patch
>
>
> The original design of Balancer is intentionally to make it run slowly so
> that the balancing activities won't affect the normal cluster activities and
> the running jobs.
> There are new use case that cluster admin may choose to balance the cluster
> when the cluster load is low, or in a maintain window. So that we should
> have an option to allow Balancer to run faster.
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