private int compare(NodeResources.DiskSpeed a, NodeResources.DiskSpeed b) {
            if (a == b) return 0;
            if (a == NodeResources.DiskSpeed.slow) return -1;
            if (b == NodeResources.DiskSpeed.slow) return 1;
            return 0;
        }
Returns a comparator comparing by memory, disk, vcpu
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/provisioning/NodeResourceComparator.java