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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8635) Define prefetcher.resultsize.max as percentage
Date Mon, 03 Jun 2013 17:17:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13673331#comment-13673331
] 

Jean-Daniel Cryans commented on HBASE-8635:
-------------------------------------------

bq. Fortunately, this is for 0.96. I agree it is a concern, but it will be a little less of
concern.

I can already see the emails titled "Upgraded to 0.96.0 but cluster doesn't start, help!"
in which we tell them they have to change their configs and they have to pick which one of
the 3 they want less of.

bq. I think it is good to scale with the amount of memory given to HBase

I thought I gave a good demonstration why this is not a good idea with bigger heaps, was there
anything you didn't agree with or do you have a counter-example?

bq. Prefetching, however, should help all the time

Well, Get-based workloads won't be faster and short Scans that require only 1 next call won't
either. Short Scans that require a few next calls will beneficiate from it but I don't see
that sort of use case needing GBs of prefetching.
                
> Define prefetcher.resultsize.max as percentage
> ----------------------------------------------
>
>                 Key: HBASE-8635
>                 URL: https://issues.apache.org/jira/browse/HBASE-8635
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Ted Yu
>            Assignee: Jimmy Xiang
>            Priority: Minor
>         Attachments: trunk-8635.patch
>
>
> Currently "hbase.hregionserver.prefetcher.resultsize.max" defines global limit for prefetching.
> The default value is 256MB.
> It would be more flexible to define this measure as a percentage of the heap.

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