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From "Yuki Morishita (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8329) LeveledCompactionStrategy should split large files across data directories when compacting
Date Wed, 19 Nov 2014 14:03:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14217926#comment-14217926
] 

Yuki Morishita commented on CASSANDRA-8329:
-------------------------------------------

[~aboudreault] Thanks for your help. We need to check if LCS will write to multiple disks
when compacting large SSTables in L0 after the patch.

> LeveledCompactionStrategy should split large files across data directories when compacting
> ------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-8329
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8329
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: J.B. Langston
>            Assignee: Marcus Eriksson
>             Fix For: 2.0.12
>
>         Attachments: 0001-get-new-sstable-directory-for-every-new-file-during-.patch
>
>
> Because we fall back to STCS for L0 when LCS gets behind, the sstables in L0 can get
quite large during sustained periods of heavy writes.  This can result in large imbalances
between data volumes when using JBOD support.  
> Eventually these large files get broken up as L0 sstables are moved up into higher levels;
however, because LCS only chooses a single volume on which to write all of the sstables created
during a single compaction, the imbalance is persisted.



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