HA

    <configuration> 
        <!--指定hdfs的nameservice为ns1，需要和core-site.xml中的保持一致 -->
        <property>
            <name>dfs.nameservices</name>
            <value>ns1</value>
        </property>

        <!-- ns1下面有两个NameNode，分别是nn1，nn2 -->
        <property>
            <name>dfs.ha.namenodes.ns1</name>
            <value>nn1,nn2</value>
        </property>

        <!-- nn1的RPC通信地址 -->
        <property>
            <name>dfs.namenode.rpc-address.ns1.nn1</name>
            <value>bigdata112:9000</value>
        </property>
        <!-- nn1的http通信地址 -->
        <property>
            <name>dfs.namenode.http-address.ns1.nn1</name>
            <value>bigdata112:50070</value>
        </property>

        <!-- nn2的RPC通信地址 -->
        <property>
            <name>dfs.namenode.rpc-address.ns1.nn2</name>
            <value>bigdata113:9000</value>
        </property>
        <!-- nn2的http通信地址 -->
        <property>
            <name>dfs.namenode.http-address.ns1.nn2</name>
            <value>bigdata113:50070</value>
        </property>

        <!-- 指定NameNode的日志在JournalNode上的存放位置 -->
        <property>
            <name>dfs.namenode.shared.edits.dir</name>
            <value>qjournal://bigdata112:8485;bigdata113:8485;/ns1</value>
        </property>
        <!-- 指定JournalNode在本地磁盘存放数据的位置 -->
        <property>
            <name>dfs.journalnode.edits.dir</name>
            <value>/root/training/hadoop-2.7.3/journal</value>
        </property>

        <!-- 开启NameNode失败自动切换 -->
        <property>
            <name>dfs.ha.automatic-failover.enabled</name>
            <value>true</value>
        </property>

        <!-- 配置失败自动切换实现方式 -->
        <property>
            <name>dfs.client.failover.proxy.provider.ns1</name>
            <value>org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider</value>
        </property>

        <!-- 配置隔离机制方法，多个机制用换行分割，即每个机制暂用一行-->
        <property>
            <name>dfs.ha.fencing.methods</name>
            <value>
                sshfence
                shell(/bin/true)
            </value>
        </property>

        <!-- 使用sshfence隔离机制时需要ssh免登陆 -->
        <property>
            <name>dfs.ha.fencing.ssh.private-key-files</name>
            <value>/root/.ssh/id_rsa</value>
        </property>

        <!-- 配置sshfence隔离机制超时时间 -->
        <property>
            <name>dfs.ha.fencing.ssh.connect-timeout</name>
            <value>30000</value>
        </property>
    </configuration>