Introduction

Distributed Systems
“ A Distributed System is a collection of independent computers that appears to its users as a single coherent system ” [Tanenbaum]
“ A Distributed System is
-a system having several computers that do not share a memory or a clock
-Communication is via message passing
-Each computer has its own OS+Memory
[Shivaratri & Singhal]

This sparks the types of MULTIPROCESSOR SYSTEM ARCHITECTURE.
Multiprocessor System Architecture Types
•Tightly Coupled Systems
•Loosely Coupled Systems

•Tightly Coupled Systems

Key point to be noticed is it shares the memory across the CUP's.Communication will be established using shared memory.

•Loosely Coupled Systems

Key Note: Loosely Coupled Systems are actually Distributed Systems. Because as per definition given above, System which does not share memory with other systems and have their own clock is Distributed system. And loosely Coupled align as per the definition.

What is the motivation to use the Distributed System/Loosely coupled System??

•Resource Sharing: Printer connected a server. Each and every individual user can avail the printer.

•Enhanced Performance: Having one machine with huge configuration(Say tera bytes) does not make sense, instead having multiple Machines distributed across the network each and every user working on his own task. Obviously makes sense.

•Improved Reliability & Availability: The word "Dedicated Machines" says all.

•Modular expandability: You can add a new user without disturbing the existing environment.