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Date: Thu, 21 Jul 2016 08:06:20 +0000 (UTC)
From: "Wei Deng (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Updated] (CASSANDRA-9829) Dynamically adjust LCS level
 sizes
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archived-at: Thu, 21 Jul 2016 08:06:22 -0000


     [ https://issues.apache.org/jira/browse/CASSANDRA-9829?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wei Deng updated CASSANDRA-9829:
--------------------------------
    Labels: compaction lcs performance  (was: compaction performance)

> Dynamically adjust LCS level sizes
> ----------------------------------
>
>                 Key: CASSANDRA-9829
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9829
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Jonathan Ellis
>              Labels: compaction, lcs, performance
>             Fix For: 3.x
>
>
> LCS works best when the top level is full.  Then 90% of reads can be served from a single sstable.  By contrast if the top level is only 10% full then 90% of reads will be served from two.  This results in worse performance as well as confused users.
> To address this, we can adjust the ideal top level size to how much data is actually in it (and set each corresponding lower level to 1/10 of the next one above).
> (This is an idea [from rocksdb|https://www.reddit.com/r/IAmA/comments/3de3cv/we_are_rocksdb_engineering_team_ask_us_anything/ct4asen].)


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