Distributed Systems

What is a distributed system?

  • A system in which hardware or software components located at networked computers communicate and coordinate their efforts

  • A collection of independant computers that appears to its users as a single computer.

Key Aspects

  • a number of components

  • communication between components

  • achieve more than the simple sum of individual components

Computer Networks vs Distributed Systems

Computer Network : Is a collection of spatially seperated, interconnected computer that exchange messages based on specific protocols. Computers are addressed by IP addresses.

Distributed System : Multiple computers on the network working together as a system. The spatial seperation of computers and communication aspects are hidden from users.

Why Distributed Systems?

Resource sharing

  • Hardware

  • Software

  • Other (Processing power, memory, bandwidth)

Benefits of resource sharing

  • Economy

  • Reliability

  • Availability

  • Scalability

Consequences of Distributed Systems

  • Concurrency : In a distributed system computers perform their tasks autonomously and communicate with other computers. Services provided by distributed systems will be accessed by multiple users. Distributed systems should take this into consideration.

  • No global clock : Clocks on individual computers operate independantly. There are limits to the accuracy with which computers in the system can synchronize their clocks.

  • Independant failures : Some components may fail while others are running. Failures of participating computers of the system is not known to others immediately.

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