1 Master(NameNode/NN) 带 N个Slaves(DataNode/DN)
HDFS/YARN/HBase
1个文件会被拆分成多个Block
blocksize：128M
130M ==> 2个Block： 128M 和 2M
NN：
1）负责客户端请求的响应
2）负责元数据（文件的名称、副本系数、Block存放的DN）的管理
DN：
1）存储用户的文件对应的数据块(Block)
2）要定期向NN发送心跳信息，汇报本身及其所有的block信息，健康状况
A typical deployment has a dedicated machine that runs only the NameNode software.
Each of the other machines in the cluster runs one instance of the DataNode software.
The architecture does not preclude running multiple DataNodes on the same machine
but in a real deployment that is rarely the case.
NameNode + N个DataNode
建议：NN和DN是部署在不同的节点上
replication factor：副本系数、副本因子
All blocks in a file except the last block are the same size