Adding 2 nodes to an existing 3-node ZooKeeper ensemble without losing the Quorum
Since many deployments may start out with 3 nodes and so little is known about how to grow a cluster from 3 memebrs to 5 members without losing the existing Quorum, here is an example of how this might be achieved.
In this example, all 5 nodes will be running on the same Vagrant host for the purpose of illustration, running on distinct configurations (ports and data directories) without the actual load of clients.
YMMV. Caveat usufructuarius.