title: Two node ZooKeeper ensemble
body: <p>We have a setup with exactly two data centers, we have exactly one machine in each data centre and we wish to have a ZooKeeper node deployed to both these machines, and for them to be clustered. We are unable to add any new machines to the cluster.</p>
  
  <p>Currently we have two ZooKeeper nodes A and B, one on machine A and one on B. We must be able to tolerate the failure of a single machine and the other ZooKeeper instance must remain operable.</p>
  
  <p>I understand from the ZooKeeper documentation that a minimum of three nodes are advised - as the coordination mechanism requires a majority of nodes to be alive to continue (in that case two).</p>
  
  <p>My question is - is it possible to get a highly available ZooKeeper deployment that consists of only two nodes?</p>