What is fault tolerance in cloud computing?

Fault tolerance refers to the ability of the system to keep functioning in even if a software or hardware failure occurs or going through a down state. It is a critical aspect to improve the realibility of a system and keep it useful for the user under all circumstances. Cloud computing enables the system to have a good fault-tolerant environment by providing on-demand services and access to a pool of configurable resources that can be utilized easily with the least management effort.

Types of faults

The overall faults can be categorized into different types based on the domain that they affect and the system's aspect that is influenced by it.

Reasons for fault occurrence

• System failure: The hardware or the software of the system crashes, causing the process of the system to abort. Hardware failure can occur due to insufficient maintenance, and software failure can occur due to stack overflow resulting in the system crashing or hanging.

• Security breach: The servers of the system are hacked by an outsider party resulting in the data being exposed and server damage. There can be different types of malicious attacks, including viruses and ransomware.

Fault-tolerant data center

A fault-tolerant data center is specially designed to provide high-level reliability for critical applications to provide continual operation even in unexpected circumstances. Cloud computing heavily relies on data centers to manage the services that deliver computing resources over the internet.

Fault tolerance through load balancing

Load balancing divides the workload and data on multiple nodes to reduce the chances of a single-point failure. They make the computing resources more resistant to disruptive behaviors by optimizing the workload distribution among the system components. Hence, none of the components experiences overloading due to equal resource distribution. When one component experiences a problem, the workload is shifted to the other components, which provides a speedy recovery from the vulnerable system downstate scenarios.

Fault tolerance through virtualization

The main purpose behind virtualization is to allow multiple users to access the same resources simultaneously. To make the virtual machines fault tolerant, the virtual machine is replicated across two separate physical servers. Hence, if one server fails, the other server takes over and keeps the virtual machine running, consequently ensuring that the services are available at all times. Adding on, there is a strong isolation between the virtual machines; therefore, if one virtual machine faces a failure, the other virtual machines are unaffected.

Fault tolerance through replication

A replication approach is adopted to prepare a sufficient backup to combat failures; therefore, systems with fault tolerance have multiple replicas for each service as a backup. If any part of the system gets defaulted or goes downstate, other instances keep it running. For example, if there is a database cluster with 5 servers that store the same information regarding data manipulation, if one of them fails due to any fault, the other can be used in its place to continue the action.

Fault tolerance through redundancy

Replication consequently brings redundancy because servers have redundant data to be used in case the main primary server is not responding. In an ideal situation, only the primary server is being utilized rest of the servers are idle. They are an alternate when the primary server fails or faces downtime to ensure continuous operation. The emergency databases also contain redundant services to be utilized in case of a midway failure of a system that is using the database.

Fault tolerance through failover and failback

Failover and failback are the two imported processes implemented to ensure continuous operation and efficient recovery from failures. Failover is the automated process of shifting to the backup resources as soon as a failure or an evident problem is detected to provide uninterrupted service. Once the primary resource is fixed, a fallback process is initiated to shift the traffic back to the primary server.

Fault tolerance through monitoring

This mechanism is used to keep a constant check on the health of the hardware system and identify performance issues. If any problem is detected, an instant recovery Fault-tolerant hardware systems employ monitoring mechanisms to continuously monitor the health and performance of components. If a failure or abnormal condition is detected, recovery mechanisms are initiated to restore the system to a functional state. This may involve restarting failed components, restoring backup data, or reallocating resources to ensure continued operation.

Note: Click here to view the topologies used in fault tolerant systems.

Summary

Fault tolerance is an essential protective feature to improve the reliability of a system and keep it useful in all circumstances. Combining all these approaches and incorporating them into the system provides a fault-tolerant system that is operational continuously and provides a better user experience. Cloud computing helps provide a network of configurable resources and services to maintain data backups without any extra setup complications. These resources are used effectively to maintain a fault-tolerant system.