[jira] [Commented] (CASSANDRA-11550) Make the fanout size for LeveledCompactionStrategy to be configurable

["Dikang Gu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-11550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15434138#comment-15434138 ] 

Dikang Gu commented on CASSANDRA-11550:
---------------------------------------

[~krummas] I got some time to test it in one of our cluster, I think the result looks promising, after I change the fanout size from 10 to 6, I see ~40% drop of the original data size, and the disk io dropped as well.

Take one node for example, before the change, the levels look like this:
SSTables in each level: [0, 12/10, 112/100, 98, 0, 0, 0, 0, 0]
SSTables in each level: [1, 11/10, 114/100, 99, 0, 0, 0, 0, 0]

After I change the fanout size to 6, it becomes:
SSTables in each level: [0, 6, 41/36, 120, 0, 0, 0, 0, 0]
SSTables in each level: [0, 6, 39/36, 123, 0, 0, 0, 0, 0]

which is more efficient, in terms of space amplification and write amplification.

[~krummas] what do you think? Thanks!

> 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: 0001-make-fanout-size-for-leveledcompactionstrategy-to-be.patch
>
>
> 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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