Model of Processor Failures

Processor failures can occur for a variety of causes, including hardware defects, software errors, power supply issues, overheating, and so on. Processor failures in distributed systems can be categorized into numerous models, each of which assumes different failure characteristics of processors. The following are some of the most often used models of processor failure in distributed systems:

• Fail-stop model: A processor fails in this model by ceasing to respond to any communication or activity. It is anticipated that a failing processor would remain dormant and will not reply to any further messages. This is the most popular and straightforward failure model in distributed systems.
• Crash failure model: In this model, a processor fails by not responding to any communication or activity, but it may still perform certain internal computations. A crashed processor is thought to be unresponsive to messages, although it can recover and rejoin the system.
• Byzantine failure model: In this paradigm, a processor can fail in any way it sees fit, such as sending wrong or malicious messages or behaving arbitrarily. In distributed systems, Byzantine failures are the most severe and complex to handle. Malicious fault are broad in nature and are Byzantine faults.

These failure models are used in the design of fault-tolerant algorithms and protocols to ensure that the system continues to function properly even if a processor fails. Each model has its own set of fault tolerance assumptions and constraints, and different models may be appropriate for different sorts of applications or systems.

Pre-requisites: What is a Distributed System?

In distributed systems, to achieve a common goal, it is required that sites reach a mutual agreement. In an example, data managers at each site must agree on whether to commit or to abort the transaction. In the agreement problems, non-faulty processors in a distributed system should be able to reach a common agreement even if certain components in the system are faulty.

A basic tool for ensuring coordination and consistency in a distributed system is an agreement protocol. Many nodes in a distributed system must collaborate to achieve a similar goal, yet due to network delays and faults, separate nodes may have different perspectives of the system state.

An agreement protocol’s purpose is to ensure that all nodes in the system finally reach the same decision, even if some nodes fail or act maliciously. There are various forms of agreement protocols, but the consensus protocol is the most well-known and commonly utilised.