private void openRAF() {
    if (DiskStoreImpl.PREALLOCATE_IF) {
      openRAF2();
      return;
    }

    try {
      ifRAF = new RandomAccessFile(ifFile, getFileMode());
      long len = ifRAF.length();
      if (len != 0) {
        ifRAF.seek(len);
      }
    } catch (IOException ex) {
      throw new DiskAccessException(
          String.format("Could not open %s.", ifFile.getPath()), ex,
          parent);
    }
  }
If the ratio of live vs. dead is not less than this constant then no need to compact.
geode-core/src/main/java/org/apache/geode/internal/cache/DiskInitFile.java