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Jonathan Ellis commented on CASSANDRA-4123: ------------------------------------------- bq. existing NTS (and also the modified implementation in CASSANDRA-3881) already prevent replicas from being placed on the same host How's that? Certainly this block from NTS looks like it will blithely assign a row to multiple vnodes on the same host: {code} // can we skip checking the rack? if (seenRacks.get(dc).size() == racks.get(dc).keySet().size()) { dcReplicas.get(dc).add(ep); replicas.add(ep); } {code} > vnodes aware Replication Strategy > ---------------------------------- > > Key: CASSANDRA-4123 > URL: https://issues.apache.org/jira/browse/CASSANDRA-4123 > Project: Cassandra > Issue Type: Sub-task > Components: Core > Reporter: Sam Overton > Assignee: Sam Overton > > The simplest implementation for this would be if NTS regarded a single host > as a distinct rack. This would prevent replicas being placed on the same > host. The rest of the logic for replica selection would be identical to NTS > (but this would be removing a level of topology hierarchy). This would be > achievable just by writing a snitch to place hosts in their own rack. > A better solution would be to add an extra level of hierarchy to NTS so that > it still supported DC & rack, and IP would be the new level at the bottom of > the hierarchy. The logic would remain largely the same. > I would very much like to build in Peter Schuller's notion of Distribution > Factor (as described in > http://www.mail-archive.com/dev@cassandra.apache.org/msg03844.html). This > requires a method of defining a "replica set" for each host and then treating > it in a similar way to a DC (ie. RF replicas are chosen from that set, > instead of from the whole cluster). -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira