private Result otherNodeHasWantedState(StorageNodeInfo nodeInfo) {
        for (var configuredNode : clusterInfo.getConfiguredNodes().values()) {
            int index = configuredNode.index();
            if (index == nodeInfo.getNodeIndex()) continue;

            State storageNodeWantedState = clusterInfo.getStorageNodeInfo(index).getUserWantedState().getState();
            if (storageNodeWantedState != UP) {
                return disallow("At most one node can have a wanted state when #groups = 1: Other storage node " +
                                index + " has wanted state " + storageNodeWantedState);
            }

            State distributorWantedState = clusterInfo.getDistributorNodeInfo(index).getUserWantedState().getState();
            if (distributorWantedState != UP) {
                return disallow("At most one node can have a wanted state when #groups = 1: Other distributor " +
                                index + " has wanted state " + distributorWantedState);
            }
        }

        return allow();
    }
Returns a disallow-result, if there is a node in the group with wanted state != UP.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java