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From "Jeremy Carroll (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13103) [ergonomics] add region size balancing as a feature of master
Date Tue, 07 Apr 2015 22:54:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484275#comment-14484275

Jeremy Carroll commented on HBASE-13103:

Few comments from my side of things. As a setup, in our architecture, we run master / slave
HBase clusters with replication setup between them.

- Since this operation is pretty impactful on performance most likely we would do this on
the slave cluster first. Switch the roles between master / slave. Then run the command on
the master. Given the time difference between when the commands were run, this could end up
with different region boundaries between the clusters -- which is not desired. So I second
the idea of  generates "reshaping plan" so it can be applied in the same manner on the slave
- Probably should think about performing a major compaction operation before the normalize
policy runs. We have a lot of tombstones on some of our clusters, which can inflate the region
size by 60%. So splitting / merging in this condition is not ideal since the condition is
temporary. Though after a compaction where you have the steady state is more realistic.

I think it's a great feature. Though most of our clusters are balanced for QPS distribution,
as CPU is one of our primary capacity planning metrics. Any tool which makes it easier to
recover from pre-splitting mistakes is welcome.

> [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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