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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7519) Support level compaction
Date Fri, 18 Jan 2013 03:46:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13556939#comment-13556939
] 

Matteo Bertozzi commented on HBASE-7519:
----------------------------------------

Why you need a different file structure? you just need a meta field associated with the file
that says "I'm in level X". All the files are already in memory with trailer and other metadata
information.

One "problem" with the LevelDB algorithm is that if the set of keys are monotonically increasing
(no overlaps between files) you end up with lots and lots of files, and at region server startup
the RS can run out of fds
                
> Support level compaction
> ------------------------
>
>                 Key: HBASE-7519
>                 URL: https://issues.apache.org/jira/browse/HBASE-7519
>             Project: HBase
>          Issue Type: New Feature
>          Components: Compaction
>            Reporter: Jimmy Xiang
>            Assignee: Jimmy Xiang
>         Attachments: level-compaction.pdf, level-compactions-notes.txt
>
>
> The level compaction algorithm may help HBase for some use cases, for example, read heavy
loads (especially, just one version is used), relative small key space updated frequently.

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