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From "Yuki Morishita (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5351) Avoid repairing already-repaired data by default
Date Mon, 03 Feb 2014 17:22:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13889646#comment-13889646
] 

Yuki Morishita commented on CASSANDRA-5351:
-------------------------------------------

[~krummas] Still reviewing your patch, but I see following problems:

* Sequential(Snapshot) repair is now default, so to use this feature users need to do 'nodetool
repair -par -inc' since I don't see incremental repair codes in snapshot repair code path.
* Performing anti-compaction in repair thread sequentially for all parent sessions seems problematic
performance-wise.

And for STCS major compaction, I prefer not to change current behavior, dropping compacted
SSTable to UNREPAIRED is fine I think. I think it is surprise for users (despite major compaction
is not recommended).

I'll look deeper but that's what I have currently.

> 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
>
>         Attachments: 5351_node1.log, 5351_node2.log, 5351_node3.log, 5351_nodetool.log
>
>
> 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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