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From "Benjamin Coverston (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5351) Avoid repairing already-repaired data by default
Date Fri, 20 Sep 2013 16:59:55 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13773178#comment-13773178
] 

Benjamin Coverston commented on CASSANDRA-5351:
-----------------------------------------------

I think this is a good idea. In fact, triggering when the un-repaired size gets to be above
some configured threshold means that repairs can be tuned for your environment. If we had
a set of SSTables that are 'repaired', another 'pending repair', and another set of 'not yet
scheduled for repair' (or queued for future repair) you could actually monitor your system
to see if repairs are 'keeping up' with your data volumes.
                
> Avoid repairing already-repaired data by default
> ------------------------------------------------
>
>                 Key: CASSANDRA-5351
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5351
>             Project: Cassandra
>          Issue Type: Task
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Lyuben Todorov
>              Labels: repair
>             Fix For: 2.1
>
>
> Repair has always built its merkle tree from all the data in a columnfamily, which is
guaranteed to work but is inefficient.
> We can improve this by remembering which sstables have already been successfully repaired,
and only repairing sstables new since the last repair.  (This automatically makes CASSANDRA-3362
much less of a problem too.)
> The tricky part is, compaction will (if not taught otherwise) mix repaired data together
with non-repaired.  So we should segregate unrepaired sstables from the repaired ones.

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