public MiniDFSCluster startMiniDFSCluster(int servers) throws Exception {
    return startMiniDFSCluster(servers, null);
  }
Start a minidfscluster.
@param servers How many DNs to start.
@see #shutdownMiniDFSCluster()
@return The mini dfs cluster created.
hbase-testing-util/src/main/java/org/apache/hadoop/hbase/HBaseTestingUtility.java