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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14215) Default cost used for PrimaryRegionCountSkewCostFunction is not sufficient
Date Wed, 12 Aug 2015 22:26:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14694308#comment-14694308
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Nick Dimiduk commented on HBASE-14215:
--------------------------------------

Seems alright to me [~gsbiju], though I haven't spent much time in stochastic balancer. These
replica weights of 10000 seem really high compared to the other weight values used in other
cost functions. Locality, for instance, is only 25, and this often has a high impact on multi-tenent
environments (so much so that we have HBASE-6721). Any chance you can test on a wider variety
of cluster sizes and rack distributions to give us a better feel for how this will behave
in practice? I'd be willing to commit with a couple more data points.

I think [~eclark] and [~enis] have spent more time on balancer, maybe they can weigh in too.

> 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
>         Attachments: 14215-v1.txt
>
>
> 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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