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From "stack (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5017) Bump the default hfile.block.cache.size because of HFileV2
Date Tue, 13 Dec 2011 21:11:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13168722#comment-13168722
] 

stack commented on HBASE-5017:
------------------------------

+1 on commit to trunk and 0.92
                
> Bump the default hfile.block.cache.size because of HFileV2
> ----------------------------------------------------------
>
>                 Key: HBASE-5017
>                 URL: https://issues.apache.org/jira/browse/HBASE-5017
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.92.0
>            Reporter: Jean-Daniel Cryans
>            Assignee: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.92.0, 0.94.0
>
>         Attachments: HBASE-5017.patch
>
>
> Here's the email I sent to the mailing list describing the problem:
> {quote}
> A thought just stuck me while I was writing down a more detailed block
> caching documentation: with HFileV2, the indexes now live in the block
> cache which means that those who upgrade may all of a sudden get
> terrible cache hit ratios because of all that memory taken by the
> indexes. This is somewhat mitigated by the fact that people don't
> usually need to keep _all_ the index blocks in memory so in the end
> we're more efficient.
> Which brings me to a question: should we set hfile.block.cache.size
> higher since indexes are now kept in the block cache? Currently it's
> set to 20%.
> Looking over my own production machines I see that the
> storefileIndexSize is around 600-700MB so that's potentially how much
> more data I'd have to block cache (more likely it's half of that
> that's really being used actively).
> What would be a good new default? 25%? 30%? How do we handle those
> that will be pushed over the BC+memstore size limit because of that
> change?
> {quote}
> I'll bump this to 25% and put in the release note the fact that people should verify
their settings before upgrading to make sure memstore+block cache isn't over 80% (meaning
they'd haven't change the block cache size but would have bumped the memstores from 40% to
60%).

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