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Date: Fri, 19 Feb 2010 20:06:28 +0000 (UTC)
From: "stack (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Resolved: (HBASE-2241) Change balancer sloppyness from 0.1
 to 0.3
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     [ https://issues.apache.org/jira/browse/HBASE-2241?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

stack resolved HBASE-2241.
--------------------------

    Resolution: Fixed
      Assignee: stack

Committed branch and trunk.

> Change balancer sloppyness from 0.1 to 0.3
> ------------------------------------------
>
>                 Key: HBASE-2241
>                 URL: https://issues.apache.org/jira/browse/HBASE-2241
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: stack
>             Fix For: 0.20.4, 0.21.0
>
>         Attachments: 2241.patch
>
>
> This is a quick workaround until we do a better balancer.
> Taking a region off line when cluster is under load is bad news.  Latency goes up as we wait on regions to come up in new locations.
> The load balancer should only cut in if the cluster is way out of alignment.
> I'd argue that 10% deviance from the avg. is not good enough reason moving regions around when cluster is under load.
> Balancer already has a knack for cutting in at most inopportune moments: during cluster startup, when new node is added to a small cluster, or moving a region just after its been opened on a node.  We'll need to do a better balancer but meantime lets just allow that region loading can be sloppier, say 20% or 30% off the average before balancer cuts in.

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