cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-3200) Repair: compare all trees together (for a given range/cf) instead of by pair in isolation
Date Tue, 13 Sep 2011 14:59:08 GMT
Repair: compare all trees together (for a given range/cf) instead of by pair in isolation
-----------------------------------------------------------------------------------------

                 Key: CASSANDRA-3200
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3200
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
            Reporter: Sylvain Lebresne
            Assignee: Sylvain Lebresne
            Priority: Minor
             Fix For: 1.0.1


Currently, repair compare merkle trees by pair, in isolation of any other tree. What that
means concretely is that if I have three node A, B and C (RF=3) with A and B in sync, but
C having some range r inconsitent with both A and B (since those are consistent), we will
do the following transfer of r: A -> C, C -> A, B -> C, C -> B.

The fact that we do both A -> C and C -> A is fine, because we cannot know which one
is more to date from A or C. However, the transfer B -> C is useless provided we do A ->
C if A and B are in sync. Not doing that transfer will be a 25% improvement in that case.
With RF=5 and only one node inconsistent with all the others, that almost a 40% improvement,
etc...

Given that this situation of one node not in sync while the others are is probably fairly
common (one node died so it is behind), this could be a fair improvement over what is transferred.
In the case where we use repair to rebuild completely a node, this will be a dramatic improvement,
because it will avoid the rebuilded node to get RF times the data it should get.

--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message