Hadoop重新做HA

1、首先在Active上执行以下命令，手动备份整个name目录：

#关闭故障自动控制器
hadoop-daemon.sh stop zkfs

#进入安全模式
hdfs dfsadmin -safemode enter

#刷新editslog到fsimage
hdfs dfsadmin -saveNamespace

2、在Standby上备份整个name和journal目录，在执行：

hadoop-daemon.sh stop zkfc
hdfs namenode -bootstrapStandby

若报以下错：
FATAL ha.BootstrapStandby: Unable to read transaction ids 10-100 from the configured shared edits storage qjournal://1.1.1.1:8485;1.1.1.2:8485/sec-hdfs-cluster. Please copy these logs into the shared edits storage or call saveNamespace on the active node.
Error: Gap in transactions. Expected to be able to read up until at least txid 10 but unable to find any edit logs containing txid 10

需要将Active整个name目录复制到Standby，然后启动namenode：

scp -r /data/hadoop/name $standby_ip:/data/hadoop
hadoop-daemon.sh start namenode