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https://issues.apache.org/jira/browse/HBASE-8517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13653180#comment-13653180
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Elliott Clark commented on HBASE-8517:
--------------------------------------
Looks like region count skew cost isn't being computed correctly.
Here's the initial cost line:
{code}2013-05-09 16:52:39,953 TRACE [IPC Server handler 1 on 60000]
org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Computed
weights for a potential balancing total = 56.488138935123175 moveCost = 0.0
regionCountSkewCost = 50.000000000000014 tableSkewCost = 0.8641975308641975
localityCost = 3.1909171075837737 memstoreSizeCost = 0.0 storefileSizeCost =
2.4330242966751934
{code}
So to me that looks like it's counting everything as being on one server...
> Stochastic Loadbalancer isn't find steady state on real clusters
> ----------------------------------------------------------------
>
> Key: HBASE-8517
> URL: https://issues.apache.org/jira/browse/HBASE-8517
> Project: HBase
> Issue Type: Bug
> Reporter: Elliott Clark
> Assignee: Elliott Clark
>
> I have a cluster that runs IT tests. Last night after all tests were done I
> noticed that the balancer was thrashing regions around.
> The number of regions on each machine is not correct.
> The balancer seems to value the cost of moving a region way too little.
> {code}
> 2013-05-09 16:34:58,920 DEBUG [IPC Server handler 4 on 60000]
> org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Finished
> computing new load balance plan. Computation took 5367ms to try 8910
> different iterations. Found a solution that moves 37 regions; Going from a
> computed cost of 56.50254222730425 to a new cost of 11.214035466575254
> 2013-05-09 16:37:48,715 DEBUG [IPC Server handler 7 on 60000]
> org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Finished
> computing new load balance plan. Computation took 4735ms to try 8910
> different iterations. Found a solution that moves 38 regions; Going from a
> computed cost of 56.612624531830996 to a new cost of 11.275763861636982
> 2013-05-09 16:38:11,398 DEBUG [IPC Server handler 6 on 60000]
> org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Finished
> computing new load balance plan. Computation took 4502ms to try 8910
> different iterations. Found a solution that moves 39 regions; Going from a
> computed cost of 56.50048461413552 to a new cost of 11.225352339003237
> {code}
> Each of those balancer runs were triggered when there was no load on the
> cluster.
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