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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:
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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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