开发者学堂课程【Hadoop 快速入门：Hadoop 官网手册】学习笔记，与课程紧密联系，让用户快速学习知识。
课程地址：https://developer.aliyun.com/learning/course/92/detail/1405
Hadoop 官网手册
内容介绍
1.Haddop 运行模式
2.基本要求
3.基本介绍
1.Haddop 运行模式
• Hadoop 运行模式包括:本地模式、伪分布式模式以及完全分布式模式。
• Hadoop 官方网站: http://hadoop.apache.org/
建议选取 2.7.2 版本
2.基本要求
Purpose
This document describes how to set up and configure a single-node Hadoop installation so that you can quickly perform simple operationsusing Hadoop MapReduce and the Hadoop Distributed File System (HDFS).
3.基本介绍
Overview
Users are encouraged to read the full set of release notes. This page provides an overview of the major changes.
Support for erasure coding in HDFS
Erasure coding is a method for durably storing data with significant space savings compared to replication. Standard encodings like Reed-Solomon (10,4) have a 1.4x space overhead, compared to the 3x overhead of standard HDFS replication.
Since erasure coding imposes additional overhead during reconstruction and performs mostly remote reads, it has traditionally been used for storing colder, less frequently accessed data. Users should consider the network and CPU overheads of erasure coding when deploying this feature.
More details are available in the HDFS Erasure Coding documentation.
