HADOOP-8143. Change distcp to have -pb on by default. Contributed by Mithun Radhakrishnan

hadoop-tools/hadoop-distcp/src/main/java/org/apache/hadoop/tools/OptionsParser.java

@@ -187,6 +187,9 @@ public class OptionsParser {
     if (command.hasOption(DistCpOptionSwitch.PRESERVE_STATUS.getSwitch())) {
       builder.preserve(
           getVal(command, DistCpOptionSwitch.PRESERVE_STATUS.getSwitch()));
+    } else {
+      // No "preserve" settings specified. Preserve block-size.
+      builder.preserve(DistCpOptions.FileAttribute.BLOCKSIZE);
     }
 
     if (command.hasOption(DistCpOptionSwitch.FILE_LIMIT.getSwitch())) {

hadoop-tools/hadoop-distcp/src/test/java/org/apache/hadoop/tools/TestOptionsParser.java

@@ -413,7 +413,7 @@ public class TestOptionsParser {
         "-f",
         "hdfs://localhost:9820/source/first",
         "hdfs://localhost:9820/target/"});
-    Assert.assertFalse(options.shouldPreserve(FileAttribute.BLOCKSIZE));
+    Assert.assertTrue(options.shouldPreserve(FileAttribute.BLOCKSIZE));
     Assert.assertFalse(options.shouldPreserve(FileAttribute.REPLICATION));
     Assert.assertFalse(options.shouldPreserve(FileAttribute.PERMISSION));
     Assert.assertFalse(options.shouldPreserve(FileAttribute.USER));