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From "Biju Nair (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-14215) Default cost used for PrimaryRegionCountSkewCostFunction is not sufficient
Date Wed, 12 Aug 2015 00:02:45 GMT
Biju Nair created HBASE-14215:
---------------------------------

             Summary: Default cost used for PrimaryRegionCountSkewCostFunction is not sufficient

                 Key: HBASE-14215
                 URL: https://issues.apache.org/jira/browse/HBASE-14215
             Project: HBase
          Issue Type: Bug
          Components: Balancer
            Reporter: Biju Nair
            Priority: Minor


Current multiplier of 500 used in the stochastic balancer cost function `PrimaryRegionCountSkewCostFunction`
to calculate the cost of  total primary replication skew doesn't seem to be sufficient to
prevent the skews (Refer HBASE-14110). We would want the default cost to be a higher value
so that skews in primary region replica has higher cost. The following is the test result
by setting the multiplier value to 10000 (same as the region replica rack cost multiplier)
on a 3 Rack 9 RS node cluster which seems to get the balancer distribute the primaries uniformly.

**Initial Primary replica distribution - using the current multiplier**	
 r1n10  102
 r1n11  85
 r1n9    88
 r2n10  120
 r2n11  120
 r2n9   124
 r3n10  135
 r3n11  124
 r3n9    129
**After long duration of read & writes - using current multiplier**	
 r1n10  102
 r1n11  85
 r1n9    88
 r2n10  120
 r2n11  120
 r2n9    124
 r3n10  135
 r3n11  124
 r3n9    129
**After manual balancing** 	
 r1n10  102
 r1n11  85
 r1n9    88
 r2n10  120
 r2n11  120
 r2n9    124
 r3n10  135
 r3n11  124
 r3n9    129
**Increased multiplier for primaryRegionCountSkewCost to 10000**	
 r1n10  114
 r1n11  113
 r1n9    114
 r2n10  114
 r2n11  114
 r2n9    113
 r3n10  115
 r3n11  115
 r3n9    115 

Setting the `PrimaryRegionCountSkewCostFunction` multiplier value to 10000 should help HBase
general use.



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