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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2149) hbase.regionserver.global.memstore.lowerLimit is too low
Date Wed, 20 Jan 2010 19:48:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12802957#action_12802957
] 

stack commented on HBASE-2149:
------------------------------

Chatting w/ J-D, it was set by me -- I think -- at 0.4 and 0.25 because of PE-itis, a condition
that comes of loading only using the PE tool.  Symptoms are inability at being able to comprehend
any other type of loading pattern.  This issue is prompted by a fella loading hbase with UUID
keys would likely spread writes nice and evenly across the cluster requiring the flushing
of many regions to go from 0.4 to 0.25.  0.4/.38?  We could try it.  Or 0.4 and 0.35?

> hbase.regionserver.global.memstore.lowerLimit is too low
> --------------------------------------------------------
>
>                 Key: HBASE-2149
>                 URL: https://issues.apache.org/jira/browse/HBASE-2149
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: Jean-Daniel Cryans
>            Assignee: Jean-Daniel Cryans
>             Fix For: 0.20.4, 0.21.0
>
>
> The default value of hbase.regionserver.global.memstore.lowerLimit of 25% is very wrong
and in almost all cases was problematic (I've seen this in at least 3 occurrences). The cost
of flushing a memstore is fairly high and when the global size reaches 40% then ALL inserts
are blocked. This means that with a heap of 1GB you could be flushing for 10-20 seconds or
worse.
> I suggest a default setting of 38% or even 40% so that only a region or two will be flushed
(the biggest ones) for maximum availability.

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