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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4683) Create config option to only cache index blocks
Date Thu, 17 Nov 2011 22:33:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13152410#comment-13152410
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Lars Hofhansl commented on HBASE-4683:
--------------------------------------

That might be a better option (always cache index blocks), looks like that'd be some amount
of refactoring (as CacheConfig.blockCache is currently null if cache size is set to 0).

The 2nd part of this is classifying index blocks (optionally) as in memory, so they are less
likely to be evicted due to churn of data blocks.

                
> Create config option to only cache index blocks
> -----------------------------------------------
>
>                 Key: HBASE-4683
>                 URL: https://issues.apache.org/jira/browse/HBASE-4683
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Lars Hofhansl
>            Priority: Minor
>             Fix For: 0.94.0
>
>         Attachments: 4683-v2.txt, 4683.txt
>
>
> This would add a new boolean config option: hfile.block.cache.datablocks
> Default would be true.
> Setting this to false allows HBase in a mode where only index blocks are cached, which
is useful for analytical scenarios where a useful working set of the data cannot be expected
to fit into the (aggregate) cache.
> This is the equivalent of setting cacheBlocks to false on all scans (including scans
on behalf of gets).
> I would like to get a general feeling about what folks think about this.
> The change itself would be simple.

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