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https://issues.apache.org/jira/browse/CASSANDRA-6496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13850048#comment-13850048
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Jonathan Ellis commented on CASSANDRA-6496:
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Can you enable debug logging in o.a.c.db.compaction and post a log sample?

> Endless L0 LCS compactions
> --------------------------
>
>                 Key: CASSANDRA-6496
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6496
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Cassandra 2.0.3, Linux, 6 nodes, 5 disks per node
>            Reporter: Nikolai Grigoriev
>
> I have first described the problem here: 
> http://stackoverflow.com/questions/20589324/cassandra-2-0-3-endless-compactions-with-no-traffic
> I think I have really abused my system with the traffic (mix of reads, heavy 
> updates and some deletes). Now after stopping the traffic I see the 
> compactions that are going on endlessly for over 4 days.
> For a specific CF I have about 4700 sstable data files right now.  The 
> compaction estimates are logged as "[3312, 4, 0, 0, 0, 0, 0, 0, 0]". 
> sstable_size_in_mb=256.  3214 files are about 256Mb (+/1 few megs), other 
> files are smaller or much smaller than that. No sstables are larger than 
> 256Mb. What I observe is that LCS picks 32 sstables from L0 and compacts them 
> into 32 sstables of approximately the same size. So, what my system is doing 
> for last 4 days (no traffic at all) is compacting groups of 32 sstables into 
> groups of 32 sstables without any changes. Seems like a bug to me regardless 
> of what did I do to get the system into this state...



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