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https://issues.apache.org/jira/browse/HDFS-8826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14703350#comment-14703350
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Chris Trezzo commented on HDFS-8826:
------------------------------------
[~arpitagarwal] [~szetszwo]
The applied patch is currently missing the -source flag in the usage message in
the balancer. See current usage message in trunk:
{code}
private static final String USAGE = "Usage: hdfs balancer"
+ "\n\t[-policy <policy>]\tthe balancing policy: "
+ BalancingPolicy.Node.INSTANCE.getName() + " or "
+ BalancingPolicy.Pool.INSTANCE.getName()
+ "\n\t[-threshold <threshold>]\tPercentage of disk capacity"
+ "\n\t[-exclude [-f <hosts-file> | <comma-separated list of hosts>]]"
+ "\tExcludes the specified datanodes."
+ "\n\t[-include [-f <hosts-file> | <comma-separated list of hosts>]]"
+ "\tIncludes only the specified datanodes."
+ "\n\t[-idleiterations <idleiterations>]"
+ "\tNumber of consecutive idle iterations (-1 for Infinite) before "
+ "exit."
+ "\n\t[-runDuringUpgrade]"
+ "\tWhether to run the balancer during an ongoing HDFS upgrade."
+ "This is usually not desired since it will not affect used space "
+ "on over-utilized machines.";
{code}
Should I file a jira or do you guys just want to post an amendment patch?
Thanks!
> Balancer may not move blocks efficiently in some cases
> ------------------------------------------------------
>
> Key: HDFS-8826
> URL: https://issues.apache.org/jira/browse/HDFS-8826
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: balancer & mover
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Fix For: 2.8.0
>
> Attachments: h8826_20150811.patch, h8826_20150816.patch,
> h8826_20150818.patch
>
>
> Balancer is inefficient in the following case:
> || Datanode || Utilization || Rack ||
> | D1 | 95% | A |
> | D2 | 30% | B |
> | D3, D4, D5 | 0% | B |
> The average utilization is 25% so that D2 is within 10% threshold. However,
> Balancer currently will first move blocks from D2 to D3, D4 and D5 since they
> are under the same rack. Then, it will move blocks from D1.
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