d Cloud Computing including Yahoo Facebook IBM etc.Hadoop mainly rely on the Hadoop Distributed File System to treat and store data. That’swhy so many companies see Hadoop Distributed File System as the research foundation ofCloud Storage and Cloud Computing. This paper detailed the treating process of HDFS and its replication mechanism.HDFS provides high security and availability as each data has many copy among differentdatanodes. Although HDFS has many datanodes it only has one metadata server which isthe bottleneck and will cause single point failure problem. This paper designed adistributed system which is based on Paxos consensus algorithm to resolve the single pointfailure problem. And we also designed an election mechanism in order to improve thesecurity and performance of the system. There are two roles in the system after electionwhich are Leader and Follower. And there has only one server as Leader and the others areseen as Follower. The Leader works as the specified acceptor and learner to coordinateand synchronize the data among all Followers. If there have N metadata servers in thesystem it can tolerate at most N 1 / 2 metadata servers of failure. As the test result shows the designed system can work if N/21 metadata servers isup. Compared to the failure of Follower the failure of Leader affects a lot more of theperformance of the system as it needs to elect a new leader while the failure of Followerdoesn’t need.Keywords: Hadoop Distributed File System Paxos Consensus Algorithm Single Point Failure Duplicate Hot Standby System II 目 录摘 要........................................................................................................... IAbstract ......................................................................................................II1 概 论1.1 Hadoop 的体系架构及其研究意义..................................................11.2 Hadoop 的研究现状..........................................................................31.3 本文的主要研究工作 ......................................................................41.4 本文的组织结构...............................................................................52 Hadoop 核心内容的研究2.1 Hadoop 的核心内容..........................................................................72.2 MapReduce 的具体实现 ...................................................................82.3 HDFS 的具体实现 ..........................................................................122.4 本章小节.........................................................................................233 HDFS 单点失效问题的应对与解决3.1 HDFS 的单点失效问题 ..................................................................243.2 Secondary Namenode 的功能 .........................................................253.3 解决单点失效问题的方法 ............................................................273.4 各种方法的分析和比较 ................................................................323.5 本章小节.........................................................................................334 基于 Paxos 分布式系统 III4.1 Paxos 一致性算法 ...........................................................................344.2 Leader 选举机制 .............................