Hadoop基础知识

浅浅的花香味﹌ 2023-02-14 00:28 36阅读 0赞

### 文章目录 ###

*  Hadoop
 *  HDFS
 *  MapReduce
 *  Hive

# Hadoop #

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# HDFS #

HDFS 分布式文件系统 读取和写入原理介绍  
HDFS中的角色  
NameNode：名称节点  
通常仅有一个，负责文件信息管理，切割文件，为文件分配指定位置保存。  
DataNode：数据阶段  
通常有多个，保存数据。

写入原理：  
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 当有文件要写入到HDFS的时候，  
 首先NameNode将文件按照指定大小切割，  
 NameNode选取合适的DataNode列表，  
 写入第一快文件，  
 同时将该文件的第一个副本写入另一个DataNode，  
 再将第二个副本写入另另外一个DataNode。  
 最后一个副本写入成功后，依次通知上一个DataNode写入完毕，  
 第一个DataNode通知NameNode写入成功后，开始写入第二份文件。

读取原理：  
当要读取文件的时候，NameNode找到该文件所有的存放位置，依次从头读取。

# MapReduce #

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# Hive #

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如图：  
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