CU-MCA-SEM II-Parallel and Distributed Computing-Second Draft

the file. As a result, if a file server with a replica is unavailable, the replica's copy is not updated.  Remote file systems allow a client computer application to access files stored on another computer. Other resources (for example, distant printers) are frequently available from a client computer via remote file systems. Sun Microsystems' Network File System (NFS) is a file sharing protocol and de facto UNIX network standard. It's commonly referred to as a \"distributed file system.\" Almost all NIX suppliers, as well as Sun's Network Formation Service (NIS), include NFS as part of their products.  Sun Microsystems (Sun) invented the Network File System (NFS) in 1984, which allows a user on a client computer can access files via a computer network in the same way that local storage is accessed.  The Andrew File System (AFS) is a distributed file system that leverages a number of trusted servers to display all client workstations with a uniform, location-transparent file name space. AFS was originally known as \"Vice,\" but it was renamed in honour of Andrew Carnegie and Andrew Mellon. Its main application is distributed computing.  In other words, AFS servers are stateful, but NFS servers are stateless. Through what is known as a call back, stateful servers in AFS enable the server to notify all clients with file types about any alterations made to that file by another client.  Hadoop applications use the Hadoop Distributed File System (HDFS) as their primary data storage system. HDFS is a distributed file system that uses a Name Node and Data Node architecture to allow high-performance data access across highly scalable Hadoop clusters. 15.7 KEYWORDS  Bandwidth - The total amount of information that can be transmitted over a network in a given time.  Dependability - The set of requirements placed on a computer system which ensures its correctness, security and fault-tolerance.  Distributed system - A system of networked computers which communicate and coordinate their actions only by-passing messages.  Fault-tolerance - The ability of a computer system to function correctly in the presence of faults in hardware, software and networks.  Performance-The set of measurements that can be applied to distributed systems to express its responsiveness to client requests, throughput and ability to meet timeliness guarantees (e.g., probability of meeting a time deadline). 301 CU IDOL SELF LEARNING MATERIAL (SLM)

15.8 LEARNING ACTIVITY 1. The Network Time Protocol service can be used to synchronize computer clocks. Explain why, even with this service, no guaranteed bound is given for the difference between two clocks. 2. Suppose that a basic disk read can sometimes read values that are different from those written. State the type of failure exhibited by a basic disk read. Suggest how this failure may be masked in order to produce a different benign form of failure. Now suggest how to mask the benign failure. 15.9 UNIT END QUESTIONS A. Descriptive Questions Short Questions 1. What is network file system? 2. What are the advantages of file replication? 3. List the three stages of Map Reduce? 4. Define fault tolerance. 5. What are the advantages of HDFS? Long Questions 1. Explain network file system. 2. Describe Andrew file system. 3. Explain the features of Hadoop 4. Explain about file replication. 5. What are the requirements of distributed file system? B. Multiple Choice Questions. 1. _____is a system for distributing the processing of large data volumes among clusters of computers. a. Hadoop b. File c. Computers d. Machine 302 CU IDOL SELF LEARNING MATERIAL (SLM)

2. ____ is a large-scale parallelization notion or approach. a. Distributed system b. File replication c. Map Reduce d. Google functions 3. Local or shared files are available to user processes operating on ____. a. Decisions b. Administrators c. Shared files d. Work stations 4. ______ Access is the most prevalent, while random access is uncommon. a. Sequential b. Random c. Basic d. Wired 5. ________are used to communicate between the NFS client and server components. a. Remote procedure calls are b. TCP c. System calls d. Client module Answers 1-a, 2- c, 3- d, 4- a, 5- a 15.10 REFERENCES Reference books  George Coulouris, Jean Dollimore, Tim Kindberg, “Distributed Systems: Concepts and Design” (4th Edition), Addison Wesley/Pearson Education. 303 CU IDOL SELF LEARNING MATERIAL (SLM)

 Pradeep K Sinha, “Distributed Operating Systems: Concepts and design”, IEEE computer society press. Text Book References  M.R. Bhujade, “Parallel Computing”, 2nd edition, New Age International Publishers2009.  Andrew S. Tanenbaum and Maarten Van Steen, “Distributed Systems: Principles and Paradigms, 2nd edition, Pearson Education, Inc., 2007, ISBN: 0-13-239227-5. Websites:  https://www.techopedia.com/definition/10062/wireless-communications  https://www.computernetworkingnotes.com/  https://www.guru99.com 304 CU IDOL SELF LEARNING MATERIAL (SLM)