HDFS-13524. Occasional "All datanodes are bad" error in TestLargeBlock#testLargeBlockSize. Contributed by Siyao Meng.

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestLargeBlock.java

@@ -50,6 +50,7 @@ public class TestLargeBlock {
   // should we verify the data read back from the file? (slow)
   static final boolean verifyData = true;
   static final byte[] pattern = { 'D', 'E', 'A', 'D', 'B', 'E', 'E', 'F'};
+  static final int numDatanodes = 3;
 
   // creates a file 
   static FSDataOutputStream createFile(FileSystem fileSys, Path name, int repl,
@@ -158,7 +159,7 @@ public class TestLargeBlock {
    * timeout here.
    * @throws IOException in case of errors
    */
-  @Test (timeout = 900000)
+  @Test (timeout = 1800000)
   public void testLargeBlockSize() throws IOException {
     final long blockSize = 2L * 1024L * 1024L * 1024L + 512L; // 2GB + 512B
     runTest(blockSize);
@@ -175,7 +176,8 @@ public class TestLargeBlock {
     final long fileSize = blockSize + 1L;
 
     Configuration conf = new Configuration();
-    MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();
+    MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
+            .numDataNodes(numDatanodes).build();
     FileSystem fs = cluster.getFileSystem();
     try {