Redundancy is actually a subset of resilience but is sometimes seen as the main way to achieve it. Actually, when you think about it, surely it’s better to put in place measures that will prevent the failure of redundant parts of your platform. Hardware failure does happen, but it’s not as common as failures by people and processes.

Redundancy comes in two varieties depending on whether human intervention is required or not. With active redundancy, if a device goes down, the system automatically reroutes the work to another device. With passive redundancy, you maintain a standby system and manually switch over.

Here’s an example of redundancy to provide availability: at home I have two Wi-Fi networks, one that is connected to my high-speed ...

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