@Override
    public boolean equals(Object o) {
        if (o instanceof StorageGroup other) {
            return this.index.equals(other.index) &&
                   this.name.equals(other.name) &&
                   this.partitions.equals(other.partitions);
        }
        return false;
    }
Returns the total number of nodes below this group
config-model/src/main/java/com/yahoo/vespa/model/content/StorageGroup.java