Distributed system

Distributed system

· A distributed system is a collection of processor located in geographical dispersal physical location.

· In this system, the workhold is distributed or divided between two or more computers that are linked together by communication network . that is the different processors communicate using communication links, such as telephone lines and buses3

· The various processors do not share memory, clock ,or peripheral devices instead each processors has its local memory.

· The purpose of distributed system is to provide an efficient and convenient environment for sharing of resources.

· Some example of distributed operating system are amoeba, angle, chorus, much, alpha kernel.

· 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.

Model 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 communication with each other for exchange of their resources.

Pros and cons of Distributed system

Pros of Distributed system

1. Resource sharing: if number of different sites is connected to one another, then a user at one site may be able to use the resource available at another site.

2. Computation speedup. A distributed system allows us to divide a computational work into sub-computations and distribute it among the various site.

3 . Load sharing. In distributed system, if a particular site is overloaded with some jobs can be moved from one site to another.

4. Reliability : if one site fails 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.

Cons of Distributed system

1. It is difficult to provide adequate security in distributed systems because the nodes as well as the connections need to be secured.
2. Some messages and data can be lost in the network while moving from one node to another.
3. The database connected to the distributed systems is quite complicated and difficult to handle as compared to a single user system.
4. Overloading may occur in the network if all the nodes of the distributed system try to send data at once.

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