[ https://issues.apache.org/jira/browse/CASSANDRA-3200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16182268#comment-16182268 ]
Marcus Eriksson commented on CASSANDRA-3200: -------------------------------------------- rebased and fixed a few forgotten todos, also removed the pointless generics in IncomingRepairStreamTracker > 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 > Reporter: Sylvain Lebresne > Assignee: Marcus Eriksson > Priority: Minor > Labels: repair > Fix For: 4.x > > > 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 was sent by Atlassian JIRA (v6.4.14#64029) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org