[jira] [Commented] (CASSANDRA-5351) Avoid repairing already-repaired data by default

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-5351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13773150#comment-13773150 ] 

Jonathan Ellis commented on CASSANDRA-5351:
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bq. I think it would be simpler to anticompact after repair

This is straightforward for STCS (bucket repaired/non-repaired separately) but less so for LCS.

Now that we're already doing STCS in L0, I suggest extending that here: reserve the levels for repaired data, and STCS until we can repair.

This implies making repair as automatic as compaction, which is a big change for us.  I think it's a lot more user friendly, but I'm not 100% confident the performance impact will be negligible.  Any better ideas?
                
> 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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