High Availability vs. Fault Tolerance | Cloud Academy

⚡️ What's the difference between #HighAvailability and #FaultTolerance?

🔥 This is a question that gets asked a lot, from people who have had years of experience within the IT industry, and those who are new and just starting out. Either way, there is clearly some confusion between the two, and understandably so. They both ultimately have the same goal, to keep your systems up and running should something fail within your architecture, but there is a difference.

👉 High Availability can be defined by maintaining a percentage of uptime that maintains operational performance, and so this can closely be aligned to an SLA. In fact, AWS has many SLAs for its services where they implement their own level of resilience and management to maintain that level of high availability.

👉 Fault Tolerance expands on High Availability to offer a greater level of protection should components begin to fail in your infrastructure. However, there are usually additional cost implications due to the greater level of resiliency offered. But the upside is that your uptime percentage increases and there is no interruption of service should 1 or more components fail.

In this brief course, our #AWS expert, Stuart Scott, answers the question: What's the difference between high availability and fault tolerance?

They both ultimately have the same goal, to keep your systems up and running should something fail within your architecture, but there is a difference and this can cause some confusion. In this course, you'll get a clear idea of what each one is, and how they differ.

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[JuriyBura]

Thanks for the video! In my view the difference between the HA and FT is that with HA, the failure of an element can be quickly recovered from (within the agreed SLA), while in FT system, the failure should not cause service interruption. From this video it almost seems like the difference is mainly in the number of component that may fail and in failure domains, while I think it is more in the effects of the failure.

[kieranosgood]

I think the key line in this was "A fault tolerant system is intrinsically highly available, but a highly available system is not necessarily fault tolerant" - every explanation I was getting kept blurring the lines on that so much because they'd say it like, yes it it this - but it isn't, and didn't seem to want to confirm that link. Thanks!

[Lawrence_Femi_Ikenna_Odedina]

Great video boss. I have a question, Using your example of an ELB with 2 ec2 instances in 2 different AZ, can the infrastructure also be fault tolerant if we added an ASG to the ELB just in case one of the ec2 instances go down the ASG can just spin up another ec2 instance?