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https://issues.apache.org/jira/browse/CASSANDRA-4310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13471954#comment-13471954
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Jonathan Ellis commented on CASSANDRA-4310:
-------------------------------------------
Looking good.
Pushed v4 to https://github.com/jbellis/cassandra/branches/4310-4 with some
changes:
- made getNextBackgroundTask synchronized. lets us not have to worry about
subsets in markCompacting (which we were handling incorrectly for user-defined
compactions -- want to fail if we can't do exactly what user asks for).
- made L0 do a best-effort job when L1 compactions get in the way of what it
would prefer to do
- skipped the initial overlapping-with-compaction difference in > L0 case since
it gets included in the check after union with overlapping in L+1
- added some @VisibleForTesting annotations
Also did some more cleanup of forceDeserialize and isCompactionInteresting in a
separate commit.
> Multiple independent Level Compactions in Parallel
> --------------------------------------------------
>
> Key: CASSANDRA-4310
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4310
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Affects Versions: 1.0.0
> Reporter: sankalp kohli
> Assignee: Yuki Morishita
> Labels: compaction, features, leveled, performance, ssd
> Fix For: 1.2.1
>
> Attachments: 4310.txt, 4310-v2.txt, 4310-v3.txt
>
>
> Problem: If you are inserting data into cassandra and level compaction cannot
> catchup, you will create lot of files in L0.
> Here is a solution which will help here and also increase the performance of
> level compaction.
> We can do many compactions in parallel for unrelated data.
> 1) For no over lapping levels. Ex: when L0 stable is compacting with L1, we
> can do compactions in other levels like L2 and L3 if they are eligible.
> 2) We can also do compactions with files in L1 which are not participating in
> L0 compactions.
> This is specially useful if you are using SSD and is not bottlenecked by IO.
> I am seeing this issue in my cluster. The compactions pending are more than
> 50k and the disk usage is not that much(I am using SSD).
> I am doing multithreaded to true and also not throttling the IO by putting
> the value as 0.
>
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