Amabri 集群 常规安装完成后 未单节点 NN 需手动升级 NN HA
步骤：
1.Check to make sure you have at least three hosts in your cluster and are running at least three ZooKeeper servers.
2.Check to make sure that the HDFS and ZooKeeper services are not in Maintenance Mode.
3.These services will be stopped and started when enabling NameNode HA. Maintenance Mode will prevent those start and stop operations from occurring. If the HDFS or ZooKeeper services are in Maintenance Mode the NameNode HA wizard will not complete successfully.
4.In Ambari Web, select Services > HDFS > Summary. （重点，很多朋友找不到开启HA服务的位置）
5.Select Service Actions and choose Enable NameNode HA.
6.The Enable HA Wizard launches. This wizard describes the set of automated and manual steps you must take to set up NameNode high availability.
7.Get Started : This step gives you an overview of the process and allows you to select a Nameservice ID. You use this Nameservice ID instead of the NameNode FQDN once HA has been set up. Click Next to proceed.
后续内容参考下官网，英文不好的使用翻译软件，不难。
官网原文参考：
http://docs.hortonworks.com/HDPDocuments/Ambari-2.1.1.0/bk_Ambari_Users_Guide/content/_how_to_configure_namenode_high_availability.html
关键步骤如图：
第二个 NN JN 骑数个 建议 3 、5 、7
启动 NN 节点上 启动 JN
启动 NN 节点上 启动 JN
启动 zkfc
