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https://issues.apache.org/jira/browse/CASSANDRA-8193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14212539#comment-14212539
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Jimmy Mårdell commented on CASSANDRA-8193:
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New patched added. I've added an enum for specifying the degree of parallelism.
This cascaded up in the code path a bit. Backward compatibility should be
maintained, at the expense of adding a few more forceRepair methods in
StorageService.
As a side note, can't we remove many of forceRepair methods in
StorageServiceMBean in 2.1? It's getting quite ugly. nodetool only uses two of
them (one with range and one without range).
> Multi-DC parallel snapshot repair
> ---------------------------------
>
> Key: CASSANDRA-8193
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8193
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Jimmy Mårdell
> Assignee: Jimmy Mårdell
> Priority: Minor
> Fix For: 2.0.12
>
> Attachments: cassandra-2.0-8193-1.txt, cassandra-2.0-8193-2.txt
>
>
> The current behaviour of snapshot repair is to let one node at a time
> calculate a merkle tree. This is to ensure only one node at a time is doing
> the expensive calculation. The drawback is that it takes even longer time to
> do the merkle tree calculation.
> In a multi-DC setup, I think it would make more sense to have one node in
> each DC calculate the merkle tree at the same time. This would yield a
> significant improvement when you have many data centers.
> I'm not sure how relevant this is in 2.1, but I don't see us upgrading to 2.1
> any time soon. Unless there is an obvious drawback that I'm missing, I'd like
> to implement this in the 2.0 branch.
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