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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3779) Allow split regions to be placed on different region servers
Date Tue, 19 Apr 2011 16:20:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021640#comment-13021640
] 

Ted Yu commented on HBASE-3779:
-------------------------------

Please refer to my blog http://zhihongyu.blogspot.com/2011/04/load-balancer-in-hbase-090.html
One of the design guidelines I follow is to not introduce randomness where possible.

The load is currently determined by the number of regions on the region server. There're plans
for improving this measure toward weighted load based on load over time.
Master runs balancer every "hbase.balancer.period" milliseconds, default 5 minutes.
My patch latches onto the most recent run of balancer where the least loaded server was recorded.
If ONE_ON_LEAST_LOADED policy is chosen, one daughter region is offloaded to that server.

HBASE-3586 has been improved though HBASE-3609.
The goal for this JIRA is to fulfill part of balancer's job at minimal cost.

> Allow split regions to be placed on different region servers
> ------------------------------------------------------------
>
>                 Key: HBASE-3779
>                 URL: https://issues.apache.org/jira/browse/HBASE-3779
>             Project: HBase
>          Issue Type: Improvement
>          Components: master
>    Affects Versions: 0.90.2
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>         Attachments: 3779.patch
>
>
> Currently daughter regions are placed on the same region server where the parent region
was.
> Stanislav Barton mentioned the idea that load information should be considered when placing
the daughter regions.
> The rationale is that the daughter regions tend to receive more writes. So it would be
beneficial to place at least one daughter region on a different region server.

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