Jens, I think you are correct that a 4 node zookeeper ensemble can be made to work but it will be slightly less resilient than a 3 node ensemble because it can only tolerate 1 failure (same as a 3 node ensemble) and the likelihood of node failures is higher because there is 1 more node that could fail. So it SHOULD be an odd number of zookeeper nodes (not MUST).
-hans > On Mar 6, 2017, at 12:20 AM, Jens Rantil <jens.ran...@tink.se> wrote: > > Hi Hans, > >> On Mon, Mar 6, 2017 at 12:10 AM, Hans Jespersen <h...@confluent.io> wrote: >> >> A 4 node zookeeper ensemble will not even work. It MUST be an odd number >> of zookeeper nodes to start. > > > Are you sure about that? If Zookeer doesn't run with four nodes, that means > a running ensemble of three can't be live-migrated to other nodes (because > that's done by increasing the ensemble and then reducing it in the case of > 3-node ensembles). IIRC, you can run four Zookeeper nodes, but that means > quorum will be three nodes, so there's no added benefit in terms of > availability since you can only loose one node just like with a three node > cluster. > > Cheers, > Jens > > > -- > Jens Rantil > Backend engineer > Tink AB > > Email: jens.ran...@tink.se > Phone: +46 708 84 18 32 > Web: www.tink.se > > Facebook <https://www.facebook.com/#!/tink.se> Linkedin > <http://www.linkedin.com/company/2735919?trk=vsrp_companies_res_photo&trkInfo=VSRPsearchId%3A1057023381369207406670%2CVSRPtargetId%3A2735919%2CVSRPcmpt%3Aprimary> > Twitter <https://twitter.com/tink>
