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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10418) give blocks of smaller store files priority in cache
Date Sat, 25 Jan 2014 02:44:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13881623#comment-13881623
] 

Sergey Shelukhin commented on HBASE-10418:
------------------------------------------

Unless file key range and scan key range don't intersect

> give blocks of smaller store files priority in cache
> ----------------------------------------------------
>
>                 Key: HBASE-10418
>                 URL: https://issues.apache.org/jira/browse/HBASE-10418
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: Sergey Shelukhin
>
> That's just an idea at this point, I don't have a patch nor plan to make one in near
future.
> It's good for datasets that don't fit in memory especially; and if scans are involved.

> Scans (and gets in absence of bloom filters' help) have to read from all store files.
Short range request will hit one block in every file.
> If small files are more likely to be entirely available in memory, on average requests
will hit less blocks from FS. 
> For scans that read a lot of data, it's better to read blocks in sequence from a big
file and blocks for small files from cache, rather than a mix of FS and cached blocks from
different files, because the (HBase) blocks of a big file would be sequential in one HDFS
block.



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