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https://issues.apache.org/jira/browse/HBASE-3373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12972870#action_12972870
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Jonathan Gray commented on HBASE-3373:
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On cluster startup in 0.90, regions are assigned in one of two ways. By
default, it will attempt to retain the previous assignment of the cluster. The
other option which I've also used is round-robin. This will evenly distribute
each table.
That plus the change to do round-robin on table create should probably cover
per-table distribution fairly well.
I think the next step in the load balancer is a major effort to switch to
something with more of a cost-based approach. I think ideally you don't need
even distribution of each table, you want even distribution of load. If one
hot table, it will get evenly balanced anyways.
One thing we could do is get rid of all random assignments and always try to do
some kind of quick load balance or round-robin. It does seem like randomness
always leads to one guy who gets an unfair share :)
> Allow regions of specific table to be load-balanced
> ---------------------------------------------------
>
> Key: HBASE-3373
> URL: https://issues.apache.org/jira/browse/HBASE-3373
> Project: HBase
> Issue Type: Improvement
> Components: master
> Affects Versions: 0.20.6
> Reporter: Ted Yu
> Fix For: 0.90.1
>
>
> From our experience, cluster can be well balanced and yet, one table's
> regions may be badly concentrated on few region servers.
> For example, one table has 839 regions (380 regions at time of table
> creation) out of which 202 are on one server.
> It would be desirable for load balancer to distribute regions for specified
> tables evenly across the cluster. Each of such tables has number of regions
> many times the cluster size.
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