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From "Dikang Gu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11550) Make the fanout size for LeveledCompactionStrategy to be configurable
Date Sun, 16 Oct 2016 02:43:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15579164#comment-15579164
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Dikang Gu commented on CASSANDRA-11550:
---------------------------------------

I test this in one of our cluster, in default fanout_size=10 case, the sstables look like
this: [1, 11/10, 135/100, 98, 0, 0, 0, 0, 0], in fanout_size=6 case, the sstables look like
this:  [1, 7/6, 38/36, 142, 0, 0, 0, 0, 0]. So in this case, after the change, the highest
level for sstables is still level 3, and we can see improvements (reduce) in space usage,
write amplification, and compaction cpu usage. I can see ~20% improvements on those areas.

Some graphs are attached.


> Make the fanout size for LeveledCompactionStrategy to be configurable
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-11550
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11550
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Compaction
>            Reporter: Dikang Gu
>            Assignee: Dikang Gu
>              Labels: lcs
>             Fix For: 3.x
>
>         Attachments: bytes_compacted.png, cpu_nice.png, write_amplification.png
>
>
> Currently, the fanout size for LeveledCompactionStrategy is hard coded in the system
(10). It would be useful to make the fanout size to be tunable, so that we can change it according
to different use cases.
> Further more, we can change the size dynamically.



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