[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=13602821#comment-13602821 ] 

Jonathan Ellis commented on CASSANDRA-5351:
-------------------------------------------

Concretely, I think a solution looks like this:

# Add a repairedAt field to SSTableMetadata.  (SSTableMetadata is immutable, but we can replace it with an identical-except-for-repaired-at copy post-repair, the way LeveledManifest.mutateLevel does.)
# Have repair skip sstables that have a non-null repairedAt by default.
# Add an option (--include-previously-repaired ?) to nodetool repair that instructs repair to include all sstables (necessary when rebuilding from a disk failure).
# Update the compaction strategies to keep repaired and non-repaired sstables separate.
                
> 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.
> 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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