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https://issues.apache.org/jira/browse/HBASE-27302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17579310#comment-17579310
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David Manning commented on HBASE-27302:
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[~claraxiong] you may find https://issues.apache.org/jira/browse/HBASE-22349
useful to you. I used it for exactly this reason - triggering a balancer run in
"sloppy" cases where a regionserver has more than 1+X% or less than 1-X%
regions, compared to the average (mean) of regions per regionserver in the
cluster.
> Adding a trigger for Stochastica Balancer to safeguard for upper bound
> outliers.
> --------------------------------------------------------------------------------
>
> Key: HBASE-27302
> URL: https://issues.apache.org/jira/browse/HBASE-27302
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Reporter: Clara Xiong
> Priority: Major
>
> In large clusters, if one outlier has a lot of regions, the calculated
> imbalance for RegionCountSkewCostFunction is quite low and often fails to
> trigger the balancer.
> For example, a node with twice average count on a 400-node cluster only
> produce an imbalance of 0.004 < 0.02(current default threshold to trigger
> balancer). An empty node also have similar effect but we have a safeguard in
> place. https://issues.apache.org/jira/browse/HBASE-24139
> We can add a safeguard for this so we don't have to lower threshold on
> larger clusters that makes the balancer more sensitive to other minor
> imbalances.
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