On Tue, Aug 5, 2014 at 3:52 AM, Rene Kochen <rene.koc...@schange.com> wrote:
> Do I have to run full repairs after this change? Because the yaml file > states: IF YOU CHANGE THE SNITCH AFTER DATA IS INSERTED INTO THE CLUSTER, > YOU MUST RUN A FULL REPAIR, SINCE THE SNITCH AFFECTS WHERE REPLICAS ARE > PLACED. > As long as you correctly configure the new snitch so that the replica sets do not change, no, you do not need to repair. Barring that, if you manage to transform the replica set in such a way that you always have one (fully repaired) replica from the old set, repair will help. I do not recommend this very risky practice. In practice the only transformation of snitch in a cluster with data which is likely to be safe is one whose result is a NOOP in terms of replica placement. In fact, the yaml file is stating something unreasonable there, because repair cannot protect against this case : - 6 node cluster, A B C D E F, RF = 2 1) Start with SimpleSnitch so that A, B have the two replicas of row key X. 2) Write row key X, value Y, to nodes A and B. 2) Change to OtherSnitch so that now C,D are responsible for row key X. 3) Repair and notice that neither C nor D answer "Y" when asked for row X. =Rob
