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https://issues.apache.org/jira/browse/CASSANDRA-5972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13756667#comment-13756667
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Jacek Lewandowski edited comment on CASSANDRA-5972 at 9/3/13 2:47 PM:
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Yes, that does assume a bunch of things. I know that it is far more complicated
than the current solution. And, I agree that a huge advantage of the solution
proposed in https://issues.apache.org/jira/browse/CASSANDRA-3200 is its rather
straightforward implementation, especially in comparison to the one described
here.
However, I've found it difficult to prove that the my solution is worse :)
For example, in a situation where one of n+1 replicas has outdated sub-range R
(and the rest are in sync), the procedure from C*-3200 will initiate n+1 data
transfers. With the algorithm described here, we would require only one data
transfer with a probability (n-1)/n, or 2 data transfers with a probability
1/n. It depends on which node starts the sequence.
was (Author: jlewandowski):
Yes, that does assume a bunch of things. I know that it is far more
complicated than the current solution. And, I agree that a huge advantage of
the solution proposed in https://issues.apache.org/jira/browse/CASSANDRA-3200
is its rather straightforward implementation, especially in comparison to the
one described here.
However, I've found it difficult to prove that the my solution is worse :)
For example, in a situation where one of n+1 replicas has outdated sub-range R,
the procedure from C*-3200 will initiate n+1 data transfers. With the algorithm
described here, we would require only one data transfer with a probability
(n-1)/n, or 2 data transfers with a probability 1/n. It depends on which node
starts the sequence.
> Reduce the amount of data to be transferred during repair
> ---------------------------------------------------------
>
> Key: CASSANDRA-5972
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5972
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jacek Lewandowski
> Priority: Minor
>
> Currently, when a validator finds a token range different in n replicas, data
> streams are initiated simultaneously between each possible pair of these n
> nodes, in both directions. It yields n*(n-1) data stream in total.
> It can be done in a sequence - Replica[1] -> R[2], R[2] -> R[3], ... , R[n-1]
> -> R[n]. After this process, the data in R[n] are up to date. Then, we
> continue: R[n] -> R[1], R[1] -> R[2], ... , R[n-2] -> R[n-1]. The active
> repair is done after 2*(n-1) data transfers performed sequentially in 2*(n-1)
> steps.
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