Storm in a Clustered Mode - Real-time Analytics with Storm and Cassandra - page 70

The Storm cluster setup
Depicted in the following figure is the Storm and Zookeeper reference cluster that we set
up in Chapter 2 , Getting Started with Your First Topology .
We have three-node Zookeeper clusters for a three-node Storm cluster (which has one Nim-
bus and two supervisors).
We are using the recommended three-node Zookeeper clusters to avoid a single point of
failure in the Storm set up.
The Zookeeper cluster should have an odd number of nodes. The reason for this require-
ment is that the Zookeeper election logic requires the leader to have an odd number of
votes, and that combination is possible only when odd nodes are in the quorum, as shown
in the following figure: