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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2015/07/18 05:56:05 UTC
[jira] [Updated] (CASSANDRA-9829) Dynamically adjust LCS level
sizes
[ https://issues.apache.org/jira/browse/CASSANDRA-9829?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jonathan Ellis updated CASSANDRA-9829:
--------------------------------------
Labels: compaction performance (was: )
> Dynamically adjust LCS level sizes
> ----------------------------------
>
> Key: CASSANDRA-9829
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9829
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Paulo Motta
> Labels: compaction, 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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