Clara Xiong created HBASE-25625:
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Summary: StochasticBalancer CostFunctions needs a better way to
evaluate resource distribution
Key: HBASE-25625
URL: https://issues.apache.org/jira/browse/HBASE-25625
Project: HBase
Issue Type: Improvement
Components: Balancer, master
Reporter: Clara Xiong
Currently CostFunctions including RegionCountSkewCostFunctions,
PrimaryRegionCountSkewCostFunctions and all load cost functions calculate how
uneven the distribution by getting the sum of deviation per region server.
TableSkewCostFunction uses the sum of the max region per server for all tables
as the measure of unevenness.
This simple implementation works when the cluster is small. But when the
cluster get larger with more region servers and regions, it doesn't work well
with hot spots or a small number of unbalanced servers.
The proposal is to use the standard deviation of the count per region server to
capture the existence of a small portion of region servers with overwhelming
load/allocation.
Patch is in test and will follow shortly.
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