"As long as you correctly configure the new snitch so that the replica sets do not change, no, you do not need to repair."
Is the following correct: The replica sets do not change if you modify the snitch from SimpleSnitch to NetworkTopologyStrategy and the topology file puts all nodes in the same data-center and rack. Thanks again! Rene 2014-08-05 20:05 GMT+02:00 Robert Coli <rc...@eventbrite.com>: > 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 > >
