public static Path getMobHome(Path rootDir) {
    return new Path(rootDir, MobConstants.MOB_DIR_NAME);
  }
Gets the root dir of the mob files under the qualified HBase root dir. It's {rootDir}/mobdir.
@param rootDir The qualified path of HBase root directory.
@return The root dir of the mob file.
hbase-server/src/main/java/org/apache/hadoop/hbase/mob/MobUtils.java