What is High availability?

Designing a system so it keeps working when a part of it fails.

In plain English

High availability means removing single points of failure. You run more than one copy of each important component, spread them across separate failure zones such as data centres, and let traffic move automatically to what is still healthy. Availability is usually quoted as a percentage of time the system is up.

Example

A service that must be up 99.9% of the year can be down for about 8.8 hours in total. At 99.99% that drops to about 53 minutes a year. Running servers in two availability zones behind a load balancer is a common way to get there.

Where you will meet it

This idea belongs to the subject area of these practice tests. We do not publish or predict real exam questions.

• CompTIA Tech+ practice tests
• KCNA practice tests

Related terms

• IaaS, PaaS and SaaS: Three ways to rent cloud computing, from raw servers (IaaS) to a platform for your code (PaaS) to a finished app (SaaS).
• Pod: The smallest unit you can deploy in Kubernetes, made of one or more containers that run together.

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