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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-953) Reevaluate HBASE-288 block caching work; should it be enabled always?
Date Fri, 24 Oct 2008 23:23:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12642568#action_12642568
] 

stack commented on HBASE-953:
-----------------------------

Enabling cache, in PE tests I see 4X improvement in sequential read test.  My guess is that
scan speed will improve again too and that compactions should go the faster also.  Downside
is that I'm OOME'ing running random read test.  Digging in some, we're creating lots of instances
of the BlockFSDataStream.  Each instance has its own ReferenceMap.  Each ReferenceMap has
1-3 entries when blocksize is 64MB.  References are cleared only when we put or get.  I'm
thinking this is not enough; that caches are not being cleared fast enough.  Trying to dig
in more.

> Reevaluate HBASE-288 block caching work; should it be enabled always?
> ---------------------------------------------------------------------
>
>                 Key: HBASE-953
>                 URL: https://issues.apache.org/jira/browse/HBASE-953
>             Project: Hadoop HBase
>          Issue Type: Task
>            Reporter: stack
>            Priority: Critical
>             Fix For: 0.19.0
>
>
> Go back and take another look at the Tom White work.  We've gotten boost in writing and
scanning because of J-D work.  HBASE-288 looks like it boosts sequential reads and perhaps
random read a little.  Take another look.

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