Distributed System Problem Solution Andrew Taneebaum & Maarten Van Steen
DISTRIBUTED SYSTEMS PRINCIPLES AND PARADIGMS
PROBLEM SOLUTIONS
ANDREW S. TANENBAUM MAARTEN VAN STEEN
Vrije Universiteit Amsterdam, The Netherlands
PRENTICE HALL
UPPER SADDLE RIVER, NJ 07458
SOLUTIONS TO CHAPTER 1 PROBLEMS
1. Q: What is the role of middleware in a distributed system? A: To enhance the distribution transparency that is missing in network operating systems. In other words, middleware aims at improving the single-system view that a distributed system should have. 2. Q: Explain what is meant by (distribution) transparency, and give examples of different types of transparency. A: Distribution transparency is the phenomenon by which distribution aspects in a system are hidden from users and applications. Examples include access transparency, location transparency, migration transparency, relocation transparency, replication transparency, concurrency transparency, failure transparency, and persistence transparency. 3. Q: Why is it sometimes so hard to hide the occurrence and recovery from failures in a distributed system? A: It is generally impossible to detect whether a server is actually down, or that it is simply slow in responding. Consequently, a system may have to report that a service is not available, although, in fact, the server is just slow. 4. Q: Why is it not always a good idea to aim at implementing the highest degree of transparency possible? A: Aiming at the highest degree of transparency may lead to a considerable loss of performance that users are not willing to accept. 5. Q: What is an open distributed system and what benefits does openness provide? A: An open distributed system offers services according to clearly defined rules. An open system is capable of easily interoperating with other open systems but also allows applications to be easily ported between different implementations of the same system. 6. Q: Describe precisely what is meant by a scalable system. A: A system is scalable with respect to either its number
PROBLEM SOLUTIONS
ANDREW S. TANENBAUM MAARTEN VAN STEEN
Vrije Universiteit Amsterdam, The Netherlands
PRENTICE HALL
UPPER SADDLE RIVER, NJ 07458
SOLUTIONS TO CHAPTER 1 PROBLEMS
1. Q: What is the role of middleware in a distributed system? A: To enhance the distribution transparency that is missing in network operating systems. In other words, middleware aims at improving the single-system view that a distributed system should have. 2. Q: Explain what is meant by (distribution) transparency, and give examples of different types of transparency. A: Distribution transparency is the phenomenon by which distribution aspects in a system are hidden from users and applications. Examples include access transparency, location transparency, migration transparency, relocation transparency, replication transparency, concurrency transparency, failure transparency, and persistence transparency. 3. Q: Why is it sometimes so hard to hide the occurrence and recovery from failures in a distributed system? A: It is generally impossible to detect whether a server is actually down, or that it is simply slow in responding. Consequently, a system may have to report that a service is not available, although, in fact, the server is just slow. 4. Q: Why is it not always a good idea to aim at implementing the highest degree of transparency possible? A: Aiming at the highest degree of transparency may lead to a considerable loss of performance that users are not willing to accept. 5. Q: What is an open distributed system and what benefits does openness provide? A: An open distributed system offers services according to clearly defined rules. An open system is capable of easily interoperating with other open systems but also allows applications to be easily ported between different implementations of the same system. 6. Q: Describe precisely what is meant by a scalable system. A: A system is scalable with respect to either its number