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Clara Xiong commented on HBASE-25739: ------------------------------------- https://github.com/apache/hbase/pull/3067 > TableSkewCostFunction need to use aggregated deviation > ------------------------------------------------------ > > Key: HBASE-25739 > URL: https://issues.apache.org/jira/browse/HBASE-25739 > Project: HBase > Issue Type: Sub-task > Components: Balancer, master > Reporter: Clara Xiong > Priority: Major > > TableSkewCostFunction uses the sum of the max deviation region per server for > all tables as the measure of unevenness. It doesn't work in a very common > scenario in operations. Say we have 100 regions on 50 nodes, two on each. We > add 50 new nodes and they have 0 each. The max deviation from the mean is 1, > compared to 99 in the worst case scenario of 100 regions on a single server. > The normalized cost is 1/99 = 0.011 < default threshold of 0.05. Balancer > wouldn't move. The proposal is to use the standard deviation of the count > per region server to detect this scenario, generating a cost of 3.1/31 = 0.1 > in this case. -- This message was sent by Atlassian Jira (v8.3.4#803005)