HDFS-208. name node should warn if only one dir is listed in dfs.name.dir. Contributed by Uma Maheswara Rao G

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1204119 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -121,6 +121,9 @@ Release 0.23.1 - UNRELEASED
 
     HDFS-2563. Some cleanup in BPOfferService. (todd)
 
+    HDFS-208. name node should warn if only one dir is listed in dfs.name.dir.
+    (Uma Maheswara Rao G via eli)
+
   OPTIMIZATIONS
 
     HDFS-2130. Switch default checksum to CRC32C. (todd)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -306,7 +306,20 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
    * @throws IOException if loading fails
    */
   public static FSNamesystem loadFromDisk(Configuration conf) throws IOException {
-    FSImage fsImage = new FSImage(conf);
+    Collection<URI> namespaceDirs = FSNamesystem.getNamespaceDirs(conf);
+    Collection<URI> namespaceEditsDirs = 
+      FSNamesystem.getNamespaceEditsDirs(conf);
+
+    if (namespaceDirs.size() == 1) {
+      LOG.warn("Only one " + DFS_NAMENODE_NAME_DIR_KEY
+          + " directory configured , beware data loss!");
+    }
+    if (namespaceEditsDirs.size() == 1) {
+      LOG.warn("Only one " + DFS_NAMENODE_EDITS_DIR_KEY
+          + " directory configured , beware data loss!");
+    }
+
+    FSImage fsImage = new FSImage(conf, namespaceDirs, namespaceEditsDirs);
     FSNamesystem namesystem = new FSNamesystem(conf, fsImage);
 
     long loadStart = now();