public void writeRawField(PdxField ft, byte[] data) {
    if (ft.isVariableLengthType()) {
      markVariableField();
    }
    updateMetaData(ft);
    os.write(data, 0, data.length);
  }
Make sure we have room to add a VLF offset.
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxWriterImpl.java