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Posted to commits@cassandra.apache.org by "Tom van der Woerdt (Jira)" <ji...@apache.org> on 2020/05/26 15:40:00 UTC

[jira] [Updated] (CASSANDRA-15836) nodetool garbagecollect could leave LCS level intact

     [ https://issues.apache.org/jira/browse/CASSANDRA-15836?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tom van der Woerdt updated CASSANDRA-15836:
-------------------------------------------
    Component/s: Local/Compaction

> nodetool garbagecollect could leave LCS level intact
> ----------------------------------------------------
>
>                 Key: CASSANDRA-15836
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15836
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local/Compaction
>            Reporter: Tom van der Woerdt
>            Priority: Normal
>
> The nodetool command `garbagecollect` will run a single-sstable compaction for every sstable in a cf, while using other sstables on the side to allow for dropping tombstoned data. However, in doing so, it resets all LCS levels back to 0, causing a significant write amplification.
> Fundamentally there's no reason why LCS levels have to be changed here, since these are single-sstable compactions. When the expected reduction in data set size is small (say, 10%) it may be preferable for sstables to remain in place instead of having to go through the entire compaction process again.



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