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Posted to dev@hbase.apache.org by "Clara Xiong (Jira)" <ji...@apache.org> on 2021/04/06 20:59:00 UTC

[jira] [Created] (HBASE-25739) TableSkewCostFunction need to use aggregated deviation

Clara Xiong created HBASE-25739:
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             Summary: 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


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.



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