HDFS-4804. WARN when users set the block balanced preference percent below 0.5 or above 1.0. Contributed by Stephen Chu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1480098 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -627,6 +627,9 @@ Release 2.0.5-beta - UNRELEASED
 
     HDFS-4784. NPE in FSDirectory.resolvePath(). (Brandon Li via suresh)
 
+    HDFS-4804. WARN when users set the block balanced preference percent below
+    0.5 or above 1.0. (Stephen Chu via atm)
+
 Release 2.0.4-alpha - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/AvailableSpaceVolumeChoosingPolicy.java

@@ -64,6 +64,16 @@ public class AvailableSpaceVolumeChoosingPolicy<V extends FsVolumeSpi>
         " = " + balancedSpaceThreshold + ", " +
         DFS_DATANODE_FSDATASET_VOLUME_CHOOSING_BALANCED_SPACE_PREFERENCE_PERCENT_KEY +
         " = " + balancedPreferencePercent);
+
+    if (balancedPreferencePercent > 1.0) {
+      LOG.warn("The value of " + DFS_DATANODE_FSDATASET_VOLUME_CHOOSING_BALANCED_SPACE_PREFERENCE_PERCENT_KEY +
+               " is greater than 1.0 but should be in the range 0.0 - 1.0");
+    }
+
+    if (balancedPreferencePercent < 0.5) {
+      LOG.warn("The value of " + DFS_DATANODE_FSDATASET_VOLUME_CHOOSING_BALANCED_SPACE_PREFERENCE_PERCENT_KEY +
+               " is less than 0.5 so volumes with less available disk space will receive more block allocations");
+    }
   }
   
   @Override