[1]??Hadoop实现了一个漫衍式文件体系（Hadoop Distributed File System），简称HDFS。HDFS有高容错性的特点，而且计划用来陈设在低廉的（low-cost）硬件上；并且它提供高吞吐量（high throughput）来会见应用措施的数据，得当那些有着超大数据集（large data set）的应用措施。HDFS放宽了（relax）POSIX的要求，可以以流的情势会见（streaming access）文件体系中的数据。
2. 多个使命是怎么被分派到多个假造机傍边的？
只有当数据量高出 1T 的大数据处理赏罚才气凸显 hadoop 的上风;??? 虽然，用 hadoop 处理赏罚 几十G、几百G 这种小数据也是可以的，只是浮现不了 hadoop的上风而已，从硬件的角度，从服从的角度都是不太值得的。
像其他框架一样，hadoop 也是分层的，? 序号③? ⑤ 就是 hadoop 中重要的构成， HDFS 认真数据存储。MapReduce 是海量数据的漫衍式计较框架。
Structured Data(hiho,sqoop)?是 hadoop 中对传统数据和 hadoop中数据彼此转化的器材。传统数据库中的数据可以导入到 hadoop中。hadoop中的数据也可以导入到传统的相关型数据库中。
HBASE?是 hadoop顶用的最多和最重要的子项目之一。虽然它也是构建于 MapReduce 和 HDFS 之上的。不外 HBASE 可以不基于 HDFS ，只是假如不基于 HDFS时就无法行使 MapReduce 计较框架了。是处理赏罚大数据读写操纵的，尤其得当一些大型在线体系。
大数据有两层寄义：第一层寄义，大数据有本身的结构形态，key-value方法。? 其它一层寄义，就是各人领略的海量数据。 之以是能成为 大数据 是由于 他是? key-value的构建方法。
HDFS文件体系，是用于打点漫衍式文件的存储与操纵的。HDFS 就为我们提供了一套机制，让海量数据可以或许漫衍在差异的计较机上。他提供言外知音就是 我们不消体谅数据是怎么存储的,HDFS 认真存储这件工作。这是我们行使 hadoop 的一个重要的缘故起因，他帮我们屏障掉一些漫衍式操纵的一些细节。
漫衍式体系中有许多台呆板，每一台呆板存储数据的一部门，我们行使 hadoop 之以是可以或许很快的计较得出功效，缘故起因很简朴 我们计较的代码会在差异的呆板上运行， 每一台呆板完成计较的一部门，由于每台呆板上存储的只是我数据的一部门。多台呆板并行计较。然后把计较功效网络过来得出最终的功效。这是Hadoop 之以是块的来源。以是 MapReduce 是我们要研究很是重要的焦点，? HDFS 的操纵是hadoop 框架屏障掉的，以是我们首要是去进修怎么去行使它。作为开拓而言，聚焦到焦点的焦点，必定是 MapReduce。 由于 MapReduce 是计较框架。也就是说数据已经存储了，我怎么计较它，这在任何一个框架中都是一个较量焦点的题目。虽然也是最有技能含量的题目。以是 假如进修hadoop 的话，有须要具体研究 MapReduce 的架构、行使、源代码等等全部的焦点环节。
5，参照网址“http://blogs.msdn.com/b/data_otaku/archive/2013/08/14/hadoop-for-net-developers.aspx” 体系进修API
using?System;??
using?System.Collections.Generic;??
using?System.Linq;??
using?System.Text;??
using?System.Threading.Tasks;??
using?Microsoft.Hadoop;??
using?Microsoft.Hadoop.MapReduce;??
using?Microsoft.Hadoop.WebClient.WebHCatClient;??
using?System.Diagnostics;??
using?System.IO;??
using?System.IO.MemoryMappedFiles;??
??
??
namespace?HadoopConsol??
{??
????class?Program??
????{??
????????static?void?Main(string[]?args)??
????????{??
????????????Stopwatch?sw?=?new?Stopwatch();??
????????????long?hadoopTime=0;??
????????????long?normalTime=0;??
??
????????????sw.Start();??
??
????????????//start?hadoop??
????????????Console.WriteLine("?????Hadoop?Process?Strating?....");??
?
????????????#region?Hadoop?time??
?
????????????#region?hadoopconnet??
??
????????????Console.WriteLine("?????Hadoop?Connect?Strating?....");??
??
????????????//establish?job?configuration??
??
????????????HadoopJobConfiguration?myConfig?=?new?HadoopJobConfiguration();??
??
????????????myConfig.InputPath?=?"/demo/simple/in";??
??
????????????myConfig.OutputFolder?=?"/demo/simple/out";??
??
??
??
????????????//connect?to?cluster??
??
????????????Uri?myUri?=?new?Uri("http://localhost");??
??
????????????string?userName?=?"hadoop";??
??
????????????string?passWord?=?null;??
??
????????????IHadoop?myCluster?=?Hadoop.Connect(myUri,?userName,?passWord);??
??
????????????hadoopTime?+=?sw.ElapsedMilliseconds;??
??
????????????Console.WriteLine("?????Hadoop?Connect?End.");??
??
????????????Console.WriteLine("?????Hadoop?Connect?time:"?+?sw.ElapsedMilliseconds);??
?
????????????#endregion??
?
?
????????????#region?hadoopmapreduce??
??
????????????sw.Reset();??
????????????sw.Start();??
??
????????????Console.WriteLine("?????Hadoop?MapReduce?Strating?....");??
??
????????????//execute?mapreduce?job??
??
????????????MapReduceResult?jobResult?=??
??
????????????????myCluster.MapReduceJob.Execute<MySimpleMapper,?MySimpleReducer>(myConfig);??
??
????????????hadoopTime?+=?sw.ElapsedMilliseconds;??
??
????????????Console.WriteLine("?????Hadoop?MapReduce?End.");??
????????????Console.WriteLine("?????Hadoop?MapReduce?Time:"+sw.ElapsedMilliseconds);??
?
????????????#endregion??
?
????????????#region?Hadoop?End??
??
????????????sw.Reset();??
????????????sw.Start();??
??
????????????Console.WriteLine("?????Hadoop?Endprocess?Strating?....");??
??
????????????//write?job?result?to?console??
??
????????????int?exitCode?=?jobResult.Info.ExitCode;??
??
??
??
????????????string?exitStatus?=?"Failure";??
??
????????????if?(exitCode?==?0)?exitStatus?=?"Success";??
??
????????????exitStatus?=?exitCode?+?"?("?+?exitStatus?+?")";??
??
????????????Console.WriteLine();??
??
????????????Console.Write("Exit?Code?=?"?+?exitStatus);??
??
????????????Console.WriteLine("?????Hadoop?Endprocess?End.");??
????????????hadoopTime?+=?sw.ElapsedMilliseconds;??
????????????Console.WriteLine("?????Hadoop?Exit?Time:"?+?sw.ElapsedMilliseconds);??
????????????Console.WriteLine("?????Hadoop?Process?All?Time:"?+?hadoopTime);??
????????????#endregion??
?
????????????#endregion??
?
?
????????????#region?Normal?time??
????????????//start?Normal??
????????????Console.WriteLine("?????Normal?Process?Strating?....");??
??
????????????sw.Reset();??
????????????sw.Start();??
??
????????????//normal?process??
????????????#region?Normal?Process??
??
????????????int?myevenCount?=?0;??
????????????int?myeventSum?=?0;??
??
????????????int?myoddCount?=?0;??
????????????int?myoddSum?=?0;??
??
????????????StreamReader?fs?=?new?StreamReader(@"c:TEMPintegers.txt");??
??
????????????while?(fs.Peek()?>=?0)??
????????????{??
????????????????string?strTemp?=?fs.ReadLine();??
????????????????if?(Int32.Parse(strTemp)?%?2?==?0)??
????????????????{??
????????????????????myevenCount++;??
????????????????????myeventSum?+=?Int32.Parse(strTemp);??
????????????????}??
????????????????else??
????????????????{??
????????????????????myoddCount++;??
????????????????????myoddSum?+=?Int32.Parse(strTemp);??
????????????????}??
????????????}??
???????????????//MemoryMappedFile?m?=?MemoryMappedFile.??
????????????Console.WriteLine("even:"?+?"t"?+?myevenCount?+?"t"?+?myeventSum);??
????????????Console.WriteLine("odd:"?+?"t"?+?myoddCount?+?"t"?+?myoddSum);??
?
????????????#endregion??
??
????????????Console.WriteLine("?????Normal?Process?End.");??
??
????????????normalTime?+=?sw.ElapsedMilliseconds;??
????????????Console.WriteLine("?????Normal?Exit?Time:"?+?sw.ElapsedMilliseconds);??
????????????Console.WriteLine("?????Normal?Process?All?Time:"?+?normalTime);??
?
????????????#endregion??
??
????????????sw.Stop();??
??
????????????Console.Read();??
??
????????}??
??
????}??
??
????public?class?MySimpleMapper?:?MapperBase??
????{??
??
????????public?override?void?Map(string?inputLine,?MapperContext?context)??
????????{??
??
????????????//interpret?the?incoming?line?as?an?integer?value??
??
????????????int?value?=?int.Parse(inputLine);??
??
????????????//determine?whether?value?is?even?or?odd??
??
????????????string?key?=?(value?%?2?==?0)???"even"?:?"odd";??
??
????????????//output?key?assignment?with?value??
??
????????????context.EmitKeyValue(key,?value.ToString());??
??
????????}??
??
????}??
??
????public?class?MySimpleReducer?:?ReducerCombinerBase??
????{??
??
????????public?override?void?Reduce(??
??
????????????string?key,?IEnumerable<string>?values,?ReducerCombinerContext?context??
??
????????????)??
????????{??
??
????????????//initialize?counters??
??
????????????int?myCount?=?0;??
??
????????????int?mySum?=?0;??
??
??
??
????????????//count?and?sum?incoming?values??
??
????????????foreach?(string?value?in?values)??
????????????{??
??
????????????????mySum?+=?int.Parse(value);??
??
????????????????myCount++;??
??
????????????}??
??
??
??
????????????//output?results??
??
????????????context.EmitKeyValue(key,?myCount?+?"t"?+?mySum);??
??
????????}??
??
??
????}??
-
} ?
来历2：http://blog.csdn.net/lansetiankong12/article/details/51086581
来历1：http://www.cnblogs.com/qq-757617012/archive/2016/11/28/6110623.html
