Hadoop大数据系列二- HDFS简介

设计目标及假设

1、Hardware Failure

2、Streaming Data Access （适用于批处理场景，不适用于交互场景）

3、Large Data Sets

4、Simple Coherency Model （数据不可修改）

5、Moving Computation is Cheaper than Moving Data

整体架构

基本组件

1、NameNode: maintains the file system namespace. Any change to the file system namespace or its properties is recorded by the NameNode. An application can specify the number of replicas of a file that should be maintained by HDFS. The number of copies of a file is called the replication factor of that file.

2、DataNode：存储对应的数据，支持一次写，多次读，不能修改。

3、Client：对应的客户端

存储策略

相关shell命令

HDFS Quotas Guide

Name Quotas

hdfs dfsadmin -setQuota N

hdfs dfsadmin -clrQuota N

Space Quotas

hdfs dfsadmin -setSpaceQuota N

hdfs dfsadmin -clrSpaceQuota N

Storage Type Quotas

hdfs dfsadmin -setSpaceQuota  -storageType

hdfs dfsadmin -clrSpaceQuota-storageType