// create test files
int numFiles = 4;
long blockSize = 1024L;
String parentDir = "/dir/";
DFSClient client = getDfsClient(cluster.getNameNode(), conf);
DatanodeInfo[] infos = client.datanodeReport(DatanodeReportType.LIVE);
ArrayList<String> rack2nodes = new ArrayList<String>();
ArrayList<DatanodeInfo> rack2di = new ArrayList<DatanodeInfo>();
for (DatanodeInfo di: infos) {
if (di.getHostName().contains("rack2")) {
rack2nodes.add(di.getName());