public File getDiskDir() {
      return diskDir;
    }
Returns the disk directory that the dynamic region factory data will be written to. Returns
null if no directory has been specified. The diskDir is only used if {@code persistBackup} is
true.

@return the disk directory that the dynamic region factory data will be written to
geode-core/src/main/java/org/apache/geode/cache/DynamicRegionFactory.java