Businesses are now operating 24/7 to meet customer demands. And it cannot afford to have interruptions in its operations at the highest demand time. Even the slightest of interruptions can lead to the loss of customer trust and create dissatisfied customers. Businesses don't want this to happen, as rightly said by Michael LeBoeuf – “A satisfied customer is the best business strategy of all.” To avoid such a scenario, a fault tolerant infrastructure is an ideal solution that reduces the losses to the businesses.

In this blog, we are going to touch base on what is Fault Tolerance and High Availability (HA), compare High Availability vs Fault Tolerance, and define the components that are used to develop a successful Fault Tolerance infrastructure. In our next blog, we will get our hands dirty to implement the Fault Tolerance infrastructure with a step-by-step guide.

What is Fault Tolerance?

Fault Tolerance means the ability of a system to function flawlessly even if one or more components have failed to perform or not working up to the mark. It is obtained by switching to a redundant system, that is being implemented at times like this to provide uninterrupted service. A Fault Tolerant infrastructure practically means 100% uptime. However, it comes at a very high cost, and businesses use it for mission-critical workloads.

Whereas, a High Availability system may have some interruptions. To represent the high availability, a sequence of 9s is utilized that denotes the level of availability.

AWS Availability LevelsDowntime in a Year
99.9% Three-nines availability8 hours and 46 minutes of downtime
99.99% Four-nines availability52 minutes and 36 seconds of downtime
99.999% Five-nines availability5 minutes and 15 seconds of downtime
100% availability [Fault Tolerance]0 minutes downtime

Fault tolerance architecture

The following features are important to know before you implement a fault tolerant infrastructure:

  • Reliability: The system must continue operating even with critical components failing.
  • Resiliency: The system can handle failure without interrupting service or data loss, and efficiently recover from the failure.
  • Redundancy: For a critical system, an identical component with the same data is in place to take over in case of any failure.
  • Monitoring: To identify any problems or issues in the production systems that may cause disruption of service.
  • Failover: The system should be able to switch to the redundant system from the active one in case of failure or poor performance.
  • Failback: The system should be able to switch back to the active component from the redundant when it has recovered from failure.

Fault Tolerance in AWS Regions and AWS Availability Zones

AWS hosts its IT infrastructure systems in different geographical locations called AWS Region, which has multiple, physically apart, AWS Availability Zones (AZs). These AZs share no service-critical components and operate to provide low latency, inexpensive network connectivity to other Availability Zones in the same region as well. Hence, they have high availability ranging from 99.9% to 99.999%. Running independent application stacks in more than one AZ within the same or different Region is important for mission critical workloads to ensure 100% uptime.

This step is to safeguard the application against downtime and have high availability.

AWS recommends the following guidelines:

  • No point of failure: Load balancing or a pair of nodes in an active standby configuration is utilized to achieve the configuration.
  • Prepare operating procedure: To respond, mitigate, or recover from a failure, an operating procedure must be defined for the manual or automatic mechanisms.
  • Database considerations: AWS RDS and Aurora offers Multi-Region/AZ deployments, that automatically replicates workloads across different AZs to handle any failovers of the existing workload due to natural disaster or data consistency.

Various service undefined feature mixes of AWS can be utilized to implement the fault tolerance in multiple AWS Availability Zones. Some of the key services can be AWS Route 53, AWS Lambda, EC2, AWS RDS, and more. We will be discussing them in the forthcoming topic.

Monitoring and Managing AWS Multi-Region Deployments

A very crucial part of implementing fault tolerance infrastructure is the 'Monitoring undefined Managing' of the infrastructure. So in case of any failure, the workload can be shifted to the redundant AWS Region. Consider the following aspects for monitoring and managing:

  • Monitoring with AWS CloudWatch: CloudWatch alarms would be helpful to monitor the resources across the AWS Availability Zones and Regions. The thresholds and triggers would detect any anomalies or issues in the resources and configure the notifications to address the issues to take the appropriate action.
  • Regular tests and failover drills: A routine performance test must be conducted to validate the failover capabilities of the infrastructure. This guarantees the workload can be switched to the redundant system in case of any AZ failure.

High Availability vs Fault Tolerance

A fault-tolerant infrastructure means 100% available with zero downtime. This system is closer to a disaster recovery system. A fault tolerant system may come at a higher cost, however, it provides a 100% uptime guarantee for mission critical workloads. A High Availability system costs much less and provides high availability ranging from Three 9s to Five 9s. Businesses that can afford downtime for their customers may prefer a High Availability infrastructure instead of paying a much higher cost for fault tolerance. However, a mission-critical workload, like a nation's security or scientific experiment involving tons of money, can not afford a single second of downtime that could jeopardize their goal.

Below is an architectural diagram depicting the High Availability vs Fault Tolerant system.

Fault tolerance architecture, High Availability Architecture, High Availability vs Fault Tolerance

Defining the Services

Let us talk about deploying a fault tolerance system in AWS. Here, we will talk about the AWS services used to successfully deploy a fault tolerance infrastructure. As for the 'How to Deply' part, we will cover it in our next blog, where we will go through a step-by-step guide with samples to showcase the deployment in AWS.

  • VPC - VPC is a Virtual Private Cloud that is built around AWS resources. VPC can also be defined as a network service that we use to establish boundaries between AWS resources.
  • Amazon Route 53 - It is a DNS service - DNS means Domain Name Service, which can translate any URL/Domain name to an IP Address. This is like a phonebook for IP Addresses.
  • AWS Lambda - Lambda runs your code on a high-availability compute infrastructure and performs all of the administration of the compute resources, including server and operating system maintenance, capacity provisioning undefined automatic scaling, and logging. With Lambda, all you need to do is supply your code in one of the language runtimes that Lambda supports.
  • API Gateway - Amazon API Gateway is an AWS service for creating, publishing, maintaining, monitoring, and securing REST, HTTP, and WebSocket APIs at any scale. API developers can create APIs that access AWS or other web services, as well as data stored in the AWS Cloud. As an API Gateway API developer, you can create APIs for use in your own client applications. Or you can make your APIs available to third-party app developers.
  • Amazon Route 53 Application Recovery Controller - Amazon Route 53 Application Recovery Controller gives you insights into whether your applications and resources are ready for recovery. The Application Recovery Controller also helps you manage and coordinate recovery for your applications across AWS Availability Zones (AZs) or Regions. These capabilities make application recoveries simpler and more reliable by reducing the manual steps required by traditional tools and processes.
  • Amazon Certificate Manager - AWS Certificate Manager (ACM) Private Certificate Authority (CA) now offers PrivateLink endpoints. ACM Private CA support for AWS PrivateLink enables you to use ACM Private CA APIs inside of your Amazon Virtual Private Cloud (VPC) and route data between your VPC and Private CA entirely within the AWS network.

End Note

Most businesses require highly available infrastructure with minimal downtime in the ranges of Three 9s to Five 9s. However, a few mission critical projects need the fault tolerance system to support their projects at all times. We have covered the basics of Fault Tolerance and High Availability in this blog, and to know how to deploy it in AWS, stay tuned for our next blog. AWS being one of the leading cloud providers, is quite reliable and available worldwide.

We at Seaflux are your dedicated partners in the ever-evolving landscape of Cloud Computing. Whether you're contemplating a seamless cloud migration, exploring the possibilities of Kubernetes deployment, or harnessing the power of AWS serverless architecture, Seaflux is here to lead the way.

Have specific questions or ambitious projects in mind? Let's discuss! Schedule a meeting with us here, and let Seaflux be your trusted companion in unlocking the potential of cloud innovation. Your journey to a more agile and scalable future starts with us.

Jay Mehta - Director of Engineering
Aashutosh Mishra

Senior Marketing Executive

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