HDFS-5517. Lower the default maximum number of blocks per file. Contributed by Aaron T. Myers.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -399,7 +399,7 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_NAMENODE_MIN_BLOCK_SIZE_KEY = "dfs.namenode.fs-limits.min-block-size";
   public static final long    DFS_NAMENODE_MIN_BLOCK_SIZE_DEFAULT = 1024*1024;
   public static final String  DFS_NAMENODE_MAX_BLOCKS_PER_FILE_KEY = "dfs.namenode.fs-limits.max-blocks-per-file";
-  public static final long    DFS_NAMENODE_MAX_BLOCKS_PER_FILE_DEFAULT = 1024*1024;
+  public static final long    DFS_NAMENODE_MAX_BLOCKS_PER_FILE_DEFAULT = 10*1000;
   public static final String  DFS_NAMENODE_MAX_XATTRS_PER_INODE_KEY = "dfs.namenode.fs-limits.max-xattrs-per-inode";
   public static final int     DFS_NAMENODE_MAX_XATTRS_PER_INODE_DEFAULT = 32;
   public static final String  DFS_NAMENODE_MAX_XATTR_SIZE_KEY = "dfs.namenode.fs-limits.max-xattr-size";

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -372,7 +372,7 @@
 
 <property>
     <name>dfs.namenode.fs-limits.max-blocks-per-file</name>
-    <value>1048576</value>
+    <value>10000</value>
     <description>Maximum number of blocks per file, enforced by the Namenode on
         write. This prevents the creation of extremely large files which can
         degrade performance.</description>