public MiniDFSCluster startMiniDFSClusterForTestWAL(int namenodePort) throws IOException {
    createDirsAndSetProperties();
    dfsCluster =
      new MiniDFSCluster(namenodePort, conf, 5, false, true, true, null, null, null, null);
    this.dfsClusterFixer = new FsDatasetAsyncDiskServiceFixer(dfsCluster);
    this.dfsClusterFixer.start();
    return dfsCluster;
  }
Start a minidfscluster. Can only create one.
@param servers How many DNs to start.
@param hosts   hostnames DNs to run on.
@see #shutdownMiniDFSCluster()
@return The mini dfs cluster created.
hbase-server/src/test/java/org/apache/hadoop/hbase/HBaseTestingUtil.java