Overview Of Distributed Systems

A distributed system is a collection of processors that do not share memory or clock. Each of the process has its own clock and memory and the processors communicate with each other through various communication lines. These processors are referred to by different names such as sites, machines, hosts, nodes, computers and so on.
A distributed system provides the user with access to various resources that the system maintains. A distributed system must provide various mechanisms for process synchronization and communication, for dealing with the deadlock problem, and other failures which are not encountered in a centralized system.

There are 4 reasons for building distributed systems :
- Resource sharing : If a 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.
- Computation speedup : If a computation can be partitioned into sub computations that can run concurrently, availability of a distributed system may allow us to distribute the computation among various sites, to run the computation concurrently.
- Reliability : If one site fails in distributed system, the remaining sites can potentially continue operating. The failure of the site must be detected by the system and the appropriate action may be needed to recover from failure.
- Communication : Information can be exchanged when several sites are connected to one another by a communication network.

The advantage of a distributed system is that these functions can be carried over great distances.