private boolean isExistingLogSegmented() {
    return !segmentsByName.firstKey().isSingleSegment();
  }
@return {@code true} if the data directory contains segments that aren't old-style single segment log files.
This should be run after a log is initialized to get the actual log segmentation state.
ambry-store/src/main/java/com/github/ambry/store/Log.java