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Posted to commits@cassandra.apache.org by "Josh McKenzie (Jira)" <ji...@apache.org> on 2021/08/24 16:18:00 UTC

[jira] [Updated] (CASSANDRA-16881) L0 compactions never recover when thousands unleveled

     [ https://issues.apache.org/jira/browse/CASSANDRA-16881?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Josh McKenzie updated CASSANDRA-16881:
--------------------------------------
    Change Category: Operability
         Complexity: Normal
             Status: Open  (was: Triage Needed)

> L0 compactions never recover when thousands unleveled
> -----------------------------------------------------
>
>                 Key: CASSANDRA-16881
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16881
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local/Compaction/STCS
>            Reporter: Josh McKenzie
>            Assignee: Josh McKenzie
>            Priority: Normal
>
> While this is somewhat mitigated by incremental repair and CASSANDRA-14388, we can still find ourselves in a scenario where we have thousands of small sstables living in L0 on STCS and get into a heavily degraded state.
> We should add a JMX flag to allow operators to flip the behaviour when doing STCS in L0 from picking the ‘hottest’ bucket to picking the largest one - this should allow us to get down to reasonable numbers of sstables in L0 quicker in this pathological case. If this proves to work particularly well we could consider making this the default in a future version. 



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