code: protected void setNamespaceID(Properties props, StorageDirectory sd)
        throws InconsistentFSStateException {
      int nsId = Integer.parseInt(getProperty(props, sd, NAMESPACE_ID));
      if (namespaceID != 0 && nsId != 0 && namespaceID != nsId) {
        throw new InconsistentFSStateException(sd.root,
            "namespaceID is incompatible with others.");
      }
      namespaceID = nsId;
    }
docs: Validate and set namespaceID version from {@link Properties}