protected static void startMiniDFSCluster(int servers) throws IOException {
    if (CLUSTER != null) {
      throw new IllegalStateException("Already started");
    }
    createDirsAndSetProperties();

    Configuration conf = UTIL.getConfiguration();

    CLUSTER = new MiniDFSCluster.Builder(conf).numDataNodes(servers).build();
    CLUSTER.waitClusterUp();
  }
Creates a directory for the cluster, under the test data
hbase-asyncfs/src/test/java/org/apache/hadoop/hbase/io/asyncfs/AsyncFSTestBase.java