hdfs-default.xml中replication相关的内容

1. <property>
     <name>dfs.replication.considerLoad</name>
     <value>true</value>
     <description>Decide if chooseTarget considers the target's load or not
     </description>
   </property>
   

    

2. <property>
     <name>dfs.block.access.token.enable</name>
     <value>false</value>
     <description>
       If "true", access tokens are used as capabilities for accessing datanodes.
       If "false", no access tokens are checked on accessing datanodes.
     </description>
   </property>
   

    

3.                                                       <!--replicationrelation 2-->
   <property>
     <name>dfs.replication</name>
     <value>3</value>
     <description>Default block replication. 
     The actual number of replications can be specified when the file is created.
     The default is used if replication is not specified in create time.
     </description>
   </property>
   
   <property>
     <name>dfs.replication.max</name>
     <value>512</value>
     <description>Maximal block replication. 
     </description>
   </property>
   
   <property>
     <name>dfs.replication.min</name>
     <value>1</value>
     <description>Minimal block replication. 
     </description>
   </property>
   
   <property>
     <name>dfs.block.size</name>
     <value>67108864</value>
     <description>The default block size for new files.</description>
   </property>
   

    

4. <property>
     <name>dfs.replication.interval</name>
     <value>3</value>
     <description>The periodicity in seconds with which the namenode computes 
     repliaction work for datanodes. </description>
   </property>
   

   
   
   

5. 因为本来的目的不是要删除replication，而是replication和erasure一起，故在hdfs-default.xml中需要添加的是erasure的property。而不是删除replication。我们可以在文件存储的过程中决定到底使用哪种机制。故要根据replicaition来找到原理。