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Date: Thu, 5 Jul 2012 23:31:35 +0000 (UTC)
From: "Jason Dai (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-6312) Make BlockCache eviction thresholds
 configurable
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    [ https://issues.apache.org/jira/browse/HBASE-6312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13407600#comment-13407600 ] 

Jason Dai commented on HBASE-6312:
----------------------------------

I think there are two different questions here:

1) Performance - whether the current values of acceptable & minimum factors make sense. It seems nobody has definitive answers, and maybe we should make these more aggressive and at least make the minimum configurable for people to experiment, just as J-D proposed.

2) User experience - whether the hfile.block.cache.size parameter provides the proper behaviors as the user would expect. It seems that most of the time the user can only use the memory size of hfile.block.cache.size * acceptable factor, which could be very confusing as the user is not aware of acceptable factor at all. What I proposed above is to evict when the cache size > hfile.block.cache.size, and block if cache size > hfile.block.cache.size * (1 + acceptable factor).

                
> Make BlockCache eviction thresholds configurable
> ------------------------------------------------
>
>                 Key: HBASE-6312
>                 URL: https://issues.apache.org/jira/browse/HBASE-6312
>             Project: HBase
>          Issue Type: Improvement
>          Components: io
>    Affects Versions: 0.94.0
>            Reporter: Jie Huang
>            Priority: Minor
>         Attachments: hbase-6312.patch
>
>
> Some of our customers found that tuning the BlockCache eviction thresholds made test results different in their test environment. However, those thresholds are not configurable in the current implementation. The only way to change those values is to re-compile the HBase source code. We wonder if it is possible to make them configurable.

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