Why Distributed Systems
- To share resources
- To bind customers and suupliers
- To allow us to do things we could not otherwise do, due to performance, scalability, reliability and availability issues
What is a Distributed System
- A distributed system is a collection of autonomous computing elements that appears to its users as a single coherent system
Charateristics of Distributed Systems
- Distributed systems can also vary in
- size
- the way in which nodes are interconnected
- the way in which node membership is handled
- Although nodes can act independently from one another, they cannot ignore one another
- Nodes are programmed to achieve common goals, and they do this by exchanging messages with each other
- To appear to users as a single coherent system, distribution transparency is an important goal of distributed systems
Fallacy(谬论) about Distributed Systems
- The network is reliable
- The network is secure
- The network is homogeneous(linux and windows)
- The topology does not change
- Latency is zero
- Bandwidth is infinite
- Transport cost is zero
- There is one administrator