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Posted to issues@hbase.apache.org by "Clara Xiong (Jira)" <ji...@apache.org> on 2021/04/12 18:34:00 UTC
[jira] [Updated] (HBASE-25739) TableSkewCostFunction need to use
aggregated deviation
[ https://issues.apache.org/jira/browse/HBASE-25739?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Clara Xiong updated HBASE-25739:
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Description: 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 aggregated deviation of the count per region server to detect this scenario, generating a cost of 3.1/31 = 0.1 in this case. (was: 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.)
> 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 aggregated 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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