When you have a ZK Ensemble a quorum of active nodes is necessary to have the entire Ensemble to work ( elect leaders, manage the cluster topology etc etc) .
The quorum is 50% living nodes +1 . If you have an ensemble of 3 nodes, the quorum is 3/2 +1 = 2 nodes . With an ensemble of 3 nodes, you can lose 1 and the ZK ensemble will continue to work. If you have an ensemble of 5 nodes, the quorum is 5/2 +1 = 3 nodes With an ensemble of 5 nodes, you can lose 2 and the ZK ensemble will continue to work. ect ect Cheers 2015-10-06 10:55 GMT+01:00 Adrian Liew <adrian.l...@avanade.com>: > Hi there, > > > > I have 3 Solr server Azure VM nodes participating in SolrCloud with ZK > installed on each of these nodes (to avoid a single point of failure with > ZK for leader election). Each Solr server is hosted in a Windows Server > 2012 R2 environment. I was told by my peer that if one zookeeper service > fails, the entire quorum fails. Hence if a quorum fails, does that mean it > will not be able to elect the leader from the remaining 2 alive Solr > servers, even if ZK services are installed in each node? > > > > I am yet to this out as this defeats the purpose of having a ZK installed > on each server. I am afraid if one node fails, a leader cannot be elected > with the remaining two available nodes. Correct me if I am wrong. > > > > Regards, > > Adrian > > > -- -------------------------- Benedetti Alessandro Visiting card - http://about.me/alessandro_benedetti Blog - http://alexbenedetti.blogspot.co.uk "Tyger, tyger burning bright In the forests of the night, What immortal hand or eye Could frame thy fearful symmetry?" William Blake - Songs of Experience -1794 England
