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https://issues.apache.org/jira/browse/HBASE-13103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14486812#comment-14486812
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Lars Hofhansl commented on HBASE-13103:
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Just reading through the comments here. Unless the "reshaper" perfectly takes
all factors into account I'd be very hesitant to run it on our clusters. With
perfect I mean that it knows about load, disk IO, etc. Since that's hard (or
impossible) I think I'd prefer to trigger this manually, as suggested in the
description. But maybe I am overly cautious.
Split decisions can be made locally and are rarely bad (unless really
excessive). Merge decisions need (a) global knowledge - not all regions may on
the same server and (b) can possibly lead to worse performance (hot regions
merged together, etc)
What we can automate is merging empty regions away.
> [ergonomics] add region size balancing as a feature of master
> -------------------------------------------------------------
>
> Key: HBASE-13103
> URL: https://issues.apache.org/jira/browse/HBASE-13103
> Project: HBase
> Issue Type: Brainstorming
> Components: Usability
> Reporter: Nick Dimiduk
> Assignee: Mikhail Antonov
> Fix For: 2.0.0, 1.1.0
>
> Attachments: HBASE-13103-v0.patch
>
>
> Often enough, folks miss-judge split points or otherwise end up with a
> suboptimal number of regions. We should have an automated, reliable way to
> "reshape" or "balance" a table's region boundaries. This would be for tables
> that contain existing data. This might look like:
> {noformat}
> Admin#reshapeTable(TableName, int numSplits);
> {noformat}
> or from the shell:
> {noformat}
> > reshape TABLE, numSplits
> {noformat}
> Better still would be to have a maintenance process, similar to the existing
> Balancer that runs AssignmentManager on an interval, to run the above
> "reshape" operation on an interval. That way, the cluster will automatically
> self-correct toward a desirable state.
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