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From "Alan Boudreault (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-8329) LeveledCompactionStrategy should split large files across data directories when compacting
Date Fri, 21 Nov 2014 13:41:34 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-8329?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alan Boudreault updated CASSANDRA-8329:
---------------------------------------
    Attachment: test_with_patch_2.0.jpg
                test_no_patch_2.0.jpg

Devs, here my test results.

h4. Test

* 12 disks of 2G of size
* Cassandra use default values for concurrent_compactors and compaction_throughput_mb_per_sec.
* Goal: Stress the server with many concurent writes  for 45-50 minutes.

h5. Results - No Patch

We can see the peak the LCS compaction of big sstables.

!test_no_patch_2.0.jpg|thumbnail!

h5. Results - With Patch

Success. There is no more peak during the compaction.

!test_with_patch_2.0.jpg|thumbnail!

Let me know if I can do anything else.


> 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,
test_no_patch_2.0.jpg, test_with_patch_2.0.jpg
>
>
> 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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