private static int nodesAdjustedForRedundancy(int nodes, int groups) {
        int groupSize = (int)Math.ceil((double)nodes / groups);
        return nodes > 1 ? (groups == 1 ? nodes - 1 : nodes - groupSize) : nodes;
    }
The number of groups this cluster has, or will have if not deployed yet.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterModel.java