1. NameNode多目录

NameNode的数据目录可以配置成多个，且每个目录存放内容相同，相当于对数据做备份，增加了可靠性

1.1. 编辑hdfs-site.xml

修改配置

<property>
    <name>dfs.namenode.name.dir</name>
    <value>file:///${hadoop.tmp.dir}/dfs/name1,file:///${hadoop.tmp.dir}/dfs/name2</value>
</property>

1.2. 重新格式化NameNode

关闭服务

1 2	stop-dfs.sh stop-yarn.sh

所有节点删除数据和日志

1 2	rm -rf /usr/local/hadoop/tmp rm -rf /usr/local/hadoop/logs/

格式化

1	hdfs namenode -format

查看生成的目录

$ tree /usr/local/hadoop/tmp/dfs/
/usr/local/hadoop/tmp/dfs/
├── name1
│   └── current
│       ├── fsimage_0000000000000000000
│       ├── fsimage_0000000000000000000.md5
│       ├── seen_txid
│       └── VERSION
└── name2    # 与name1完全一致
    └── current
        ├── fsimage_0000000000000000000
        ├── fsimage_0000000000000000000.md5
        ├── seen_txid
        └── VERSION

1.3. 启动HDFS并查看NameNode

启动服务

1	start-dfs.sh

上传文件

1	hdfs dfs -put 1.txt /

查看目录树，name1与name2仍完全一致

$ tree -a /usr/local/hadoop/tmp/dfs/  
/usr/local/hadoop/tmp/dfs/
├── data
│   ├── current
│   │   ├── BP-774990081-192.168.57.101-1551014303666
│   │   │   ├── current
│   │   │   │   ├── finalized
│   │   │   │   │   └── subdir0
│   │   │   │   │       └── subdir0
│   │   │   │   │           ├── blk_1073741825
│   │   │   │   │           └── blk_1073741825_1001.meta
│   │   │   │   ├── rbw
│   │   │   │   └── VERSION
│   │   │   ├── dncp_block_verification.log.curr
│   │   │   ├── dncp_block_verification.log.prev
│   │   │   └── tmp
│   │   └── VERSION
│   └── in_use.lock
├── name1
│   ├── current
│   │   ├── edits_0000000000000000001-0000000000000000008
│   │   ├── edits_inprogress_0000000000000000009
│   │   ├── fsimage_0000000000000000000
│   │   ├── fsimage_0000000000000000000.md5
│   │   ├── fsimage_0000000000000000008
│   │   ├── fsimage_0000000000000000008.md5
│   │   ├── seen_txid
│   │   └── VERSION
│   └── in_use.lock
└── name2
    ├── current
    │   ├── edits_0000000000000000001-0000000000000000008
    │   ├── edits_inprogress_0000000000000000009
    │   ├── fsimage_0000000000000000000
    │   ├── fsimage_0000000000000000000.md5
    │   ├── fsimage_0000000000000000008
    │   ├── fsimage_0000000000000000008.md5
    │   ├── seen_txid
    │   └── VERSION
    └── in_use.lock