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https://issues.apache.org/jira/browse/ACCUMULO-2488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13938392#comment-13938392
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Mike Drob commented on ACCUMULO-2488:
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The default balancer will allow a difference of up to the number of tables
before it starts moving tablets. In this case it sounds like you had at least 4
(metadata, trace, old table, active table) and the largest difference was 3
(5-2), so the balancer did not do anything, as intended.
> Concurrent randomwalk balance check needs refinement
> ----------------------------------------------------
>
> Key: ACCUMULO-2488
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2488
> Project: Accumulo
> Issue Type: Test
> Components: test
> Affects Versions: 1.4.4
> Reporter: Bill Havanki
> Assignee: Bill Havanki
> Priority: Minor
> Labels: randomwalk, test
>
> The check for balanced tablets in the randomwalk Concurrent test too easily
> fails.
> Here is a real-life example from the test for the number of tablets across
> five tablet servers: 2, 5, 2, 2, 3. (An old unrelated table plays into these
> totals.) This produces a mean of 2.8. The cluster is considered unbalanced by
> the test when any server's count differs from the mean by the larger of 1 or
> the mean divided by 5. In this case, 2.8/5 is less than 1, so the second
> tablet server fails since it has more than 3.8 tablets. Even a 4 would fail.
> Part of the problem in this particular case is that there are so few tablets,
> and so few tablet servers. The cluster also seems happy to leave these counts
> as is, as I continue to check it, so the test's definition of unbalanced is
> too narrow.
> The test needs to be refined to detect unbalanced conditions with a
> statistically decent calculation.
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