Distributed Operating System

Distributed Operating System

• A distributed system is a collection of processors located in geographical dispersed physical location.
• In this system, the workload is distributed or divided between two or more computers that are linked together by a communication network. That is, the different processors communicate using communication links, such as telephone lines and buses.
• The various processors do not share memory, clock, or peripheral devices. Instead each processor has its own local memory.
• The processors in a distributed system vary in size and function. They may include small microprocessors, workstations microcomputers, mainframe computers and large general purpose computers. The various processors are also called as sites, nodes, hosts or machine.
• The purpose of distributed system is to provide an efficient and convenient environment for sharing of resources.
• Some examples of distributed operating system are Amoeba, Angle, Chorus, Mach, Alpha Kernel.

Models of Distributed Operating System

The design of distributed operating system is based on two models:

1. Client-server model
2. Peer-to-peer model

1. Client-server model:

In client server model, the client send a resource request to the server and the server in turn provides the requested resources as the response back to client.

2. Peer-to-peer model:

In peer-to-peer model, all the computers behave as clients. These clients communicate with each other for exchange of their resources.

Advantages of distributed systems

1. Resource Sharing:

If number of different sites are connected to one another, then a user at one site may be able to use the resources available at another site. Resource sharing provides mechanisms for sharing files at remote sites, processing information in distributed database, printing files at remote site etc.

2. Computation Speedup:

A distributed system allows us to divide a computational work into sub-computations and distribute it among the various sites. These sub computations can be run concurrently and thereby increases the speed of computation.

3. Load Sharing:

In distributed system, if a particular site is overloaded with some jobs a job can be moved from one site to another. Hence load of one site can be shared by another site.

4. Reliability:

If one site tails in a distributed system, the remaining sites can continue operating, giving the system better reliability.

5. Communication:

When several sites are connected to one another by a communication network, the users at different sites can exchange information.