@Override
  protected long getSizeToCheck(final int tableRegionsCount) {
    return tableRegionsCount == 1 ? this.initialSize : getDesiredMaxFileSize();
  }
@return flushSize * 2 if there's exactly one region of the table in question found on this
        regionserver. Otherwise max file size. This allows a table to spread quickly across
        servers, while avoiding creating too many regions.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/SteppingSplitPolicy.java