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From "Charlie Groves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5351) Avoid repairing already-repaired data by default
Date Mon, 20 May 2013 23:59:16 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13662476#comment-13662476
] 

Charlie Groves commented on CASSANDRA-5351:
-------------------------------------------

Won't nodes other than the coordinator only have portions of their sstables repaired? If node
A is coordinating repair and is responsible for keys 1-50 and node B is responsible for keys
26-75, B won't get repairs for 51-75 during the repair A runs. If B marked its sstables as
repaired, it'd never repair 51-75. 

Also, if A is coordinating and there are replicas for 26-50 other than B, B won't get repairs
for that range from replicas other than A. It would still have invalid data in that range
if one of the other replicas had the correct data.
                
> 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
>              Labels: repair
>             Fix For: 2.0
>
>
> 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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