private Result checkRedundancy(DistributorNodeInfo distributorNodeInfo, Node node) {
        Integer minReplication = minReplication(distributorNodeInfo).get(node.getIndex());
        return verifyRedundancy(distributorNodeInfo, minReplication, node.getIndex());
    }
Verifies that storage nodes and distributors are up (or retired).
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java