Lecture 4

Question 1

What is a distributed system?

Answer 1

A Distributed system is a collection of loosely coupled nodes interconnected by a communication network.

From the point of view of a specific node in a distributed system, its own resources are local, whereas the rest of the nodes and their respective resources are remote.

Question 2

Features of nodes?

Answer 2

The nodes in a distributed system may vary in size and function (i.e)

They are also referred to by a number of names (i.e) depending on the context in which they are mentioned.

We mainly use site to indicate the location of a machine and node to refer to a specific system at site

Question 3

Why do we need distributed systems:

Resource sharing

Answer 3

Resource sharing: A user at 1 site may be able to use the resource available at another. For example, a user at site A may be using a laser printer located at site B. Meanwhile, a user at B may access a file that resides at A

Question 4

Why do we need distributed systems:

Computation speedup

Answer 4

Computation speedup: Subcompuatations can be distributed among the various sites and run concurrently. If a particular site is overloaded, jobs can be moved to other sites (load sharing or job migration)

Question 5

Why do we need distributed systems:

Reliabality

Answer 5

Reliabality: If one site` fails in a distributed system, the remaining sites can continue operation, giving the system better relabaility. With enough redundancy (in both hardware and data) the system can continue operation, even if some of it sites have failed

Question 6

Why do we need distributed systems:

Communication

Answer 6

Communication: Users at various sites can exchange information. At a low level, message are passed between systems. All higher-level functionality of a standalone system can be expanded to encompass the distributed system (i.e. file transfer, login, mail and remote procedure calls (RPCs))

Question 7

Advantages of Distributed systems?

Answer 7

Reliable, High fault tolerance
Scalability
Flexibility
Speedup
Openness
High Performance

Question 8

Disadvantages of Distributed systems?

Answer 8

Difficult troubleshooting
Less software support
High Network infrastructure costs
Security issues

Question 9

Examples of distributed systems?

Answer 9

Grid computing
Cloud computing
Blockchain
Internet of Things
DDoS