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https://issues.apache.org/jira/browse/HBASE-12451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14206040#comment-14206040
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Qiang Tian commented on HBASE-12451:
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Thanks Duo, forgot that. 
with default values, it looks the region split size will use upper limit after 
3 regions.
according to http://hbase.apache.org/book/ops.capacity.html, region count and 
region size are most important factors, but there is no clear answer for region 
count?

bq. If we already have 240 regions of a table, and there is only one region of 
this table on a regionserver, should the region have a small split size?

the regions should be evenly spread across RS(8 RS in that case)






> IncreasingToUpperBoundRegionSplitPolicy may cause unnecessary region splits 
> in rolling update of cluster
> --------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-12451
>                 URL: https://issues.apache.org/jira/browse/HBASE-12451
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Liu Shaohui
>            Assignee: Liu Shaohui
>            Priority: Minor
>             Fix For: 2.0.0
>
>
> Currently IncreasingToUpperBoundRegionSplitPolicy is the default region split 
> policy. In this policy, split size is the number of regions that are on this 
> server that all are of the same table, cubed, times 2x the region flush size.
> But when unloading regions of a regionserver in a cluster using 
> region_mover.rb, the number of regions that are on this server that all are 
> of the same table will decrease, and the split size will decrease too, which 
> may cause the left region split in the regionsever. Region Splits also 
> happens when loading regions of a regionserver in a cluster. 
> A improvment may set a minimum split size in 
> IncreasingToUpperBoundRegionSplitPolicy
> Suggestions are welcomed. Thanks~



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