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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-862) region balancing is clumsy
Date Tue, 30 Dec 2008 17:00:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12659849#action_12659849

Andrew Purtell commented on HBASE-862:


Seeing this on our cluster as well. Master starts up in safe mode. All HRS start up and check
in. Then initial assignments start. Assignment is lumpy -- average load should be e.g. 40,
some HRS get e.g. 80 initial assignments. They report as overloaded, so then regions are closed
and moved almost as soon as they are opened. Compaction/split load is increased unnecessarily.

Also seeing asserts about illegal state transitions from the Master.

All regions do come up assigned and HRS are evenly loaded after a while, unless compaction/split
load overwhelms DFS. Then usually there are a few regions that did not deploy correctly that
have to be manually (re)deployed with close_region from the shell. 

> region balancing is clumsy
> --------------------------
>                 Key: HBASE-862
>                 URL: https://issues.apache.org/jira/browse/HBASE-862
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
> Daniel Leffel has an install of 500 regions on 4 nodes.  He's running 0.2.0.
> On restart, load balancing is running while the 600 regions are being initially opened.
 Makes for churn.  Load balancing should wait before it cuts in.
> Have also seen on occasion that it will not find equilibrium after a restart.
> Adding a node is catastrophic.  >20% of the regions were closed and were taking the
longest time to show up on the new server.  I would think that the region balancing would
work in more sophisticated and gradual manner.

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