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From "Michael Theroux (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4905) Repair should exclude gcable tombstones from merkle-tree computation
Date Fri, 24 May 2013 18:52:22 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13666542#comment-13666542
] 

Michael Theroux commented on CASSANDRA-4905:
--------------------------------------------

We have a large variety of usecases that have different table characteristics.  We do have
tables with wide rows, and do have tables with ttls, but don't have tables with wide rows
and ttls together. 

Nodetool ring shows we have 280GB per node, or a little less.

If I'm understanding the issue though, all you would need is large numbers of tombstones getting
compacted and deleted from one node, and not the others.  The table that has been giving us
the most grief uses LeveledCompaction, which makes a guarantee that at most 10% of space will
be wasted by obsolete rows.  Given that there is no guarantee that the 10% of rows on one
node overlaps with the 10% of rows on another node, could it be possible that this causes
the massive repairs?  
                
> Repair should exclude gcable tombstones from merkle-tree computation
> --------------------------------------------------------------------
>
>                 Key: CASSANDRA-4905
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4905
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Christian Spriegel
>            Assignee: Sylvain Lebresne
>             Fix For: 1.2.0 beta 3
>
>         Attachments: 4905.txt
>
>
> Currently gcable tombstones get repaired if some replicas compacted already, but some
are not compacted.
> This could be avoided by ignoring all gcable tombstones during merkle tree calculation.
> This was discussed with Sylvain on the mailing list:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/repair-compaction-and-tombstone-rows-td7583481.html

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