private void validateGroupSiblings(String cluster, StorageGroup group) {
            Set<String> siblings = new HashSet<>();
            for (StorageGroup g : group.getSubgroups()) {
                String name = g.getName();
                if (siblings.contains(name)) {
                    throw new IllegalArgumentException("Cluster '" + cluster + "' has multiple groups " +
                                                       "with name '" + name +
                                                       "' in the same subgroup. Group sibling names must be unique.");
                }
                siblings.add(name);
            }
        }
Returns of memory reserved on a host. Memory is reserved for the jvm if the cluster is combined
config-model/src/main/java/com/yahoo/vespa/model/content/cluster/ContentCluster.java