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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3799) Provide more accurate check for super underloaded region server in load balancer
Date Tue, 19 Apr 2011 17:02:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021661#comment-13021661
] 

stack commented on HBASE-3799:
------------------------------

A general comment on balancing (that probably fits better elsewhere than as a comment on this
issue) is that we need 'smoothing' of region move.... Yesterday we brought a regionserver
back online into a smallish cluster that was under load and the balance run unloaded a bunch
of regions all in the one go which put a dent in the throughput;  it'd be sweet if the balancer
ran at an appropriate 'rate'.  When under load, it should move regions 'gently' rather than
all as a big bang (the decommission script will move a region at a time, verifying it deployed
in its new location before moving another... this can take ages to complete but its proven
minimally disruptive to loadings)

> Provide more accurate check for super underloaded region server in load balancer
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-3799
>                 URL: https://issues.apache.org/jira/browse/HBASE-3799
>             Project: HBase
>          Issue Type: Bug
>          Components: mapreduce
>    Affects Versions: 0.90.2
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>
> HBASE-3609 used simple check for region server which recently joined the cluster so that
both young and old regions from other region servers are assigned to it.
> The check was too strict.
> 1 or more region may be assigned to this server before load balancer performs rebalancing.
> The next time balancer runs, it wouldn't treat this server as seriously underloaded correctly
and assign a lot of young regions to it.
> We can use threshold over the number of regions to avoid such issue.

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