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https://issues.apache.org/jira/browse/HBASE-10761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14006588#comment-14006588
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Elliott Clark commented on HBASE-10761:
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The process of computing a balance can be very expensive. We should be very
careful to make sure that we can't get into a situation where the balancer will
do a full pass through all option, determine that nothing needs to move, and
loop through again next time.
> StochasticLoadBalancer still uses SimpleLoadBalancer's needBalance logic
> ------------------------------------------------------------------------
>
> Key: HBASE-10761
> URL: https://issues.apache.org/jira/browse/HBASE-10761
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Affects Versions: 0.98.0
> Reporter: Victor Xu
> Fix For: 0.99.0
>
> Attachments: HBASE_10761.patch, HBASE_10761_v2.patch
>
>
> StochasticLoadBalancer has become the default balancer since 0.98.0. But its
> balanceCluster method still uses the BaseLoadBalancer.needBalance() which is
> originally designed for SimpleLoadBalancer. It's all based on the number of
> regions on the regionservers.
> This can cause such a problem: when the cluster has some Hot Spot Region, the
> balance process may not be triggered because the numbers of regions on the
> RegionServers are averaged.
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