21. Disaster Recovery

RTO and RPO numbers apply to localized outages, but when setting your RTO and RPO, you must take into account worst case scenarios. The term Disaster Recover is used to describe a more widespread failure. In AWS, if you normally run your services in one region, a large enough failure to make you move your system to another region would be a Disaster Recovery (DR) event.

Disaster Recovery usually involves the wholesale moving of your platform from one place to another. Outside of AWS, you might have to move to a backup data center. Inside AWS, you can move to a different region. Disaster recovery is not something you can do after an incident occurs to take down your primary region. If you have not prepared in advance, you will have no choice but to wait for that region to recover. To be prepared ahead of time, consider all of the things you will need to restart your platform in a new home. What saved state do you need, what application software, what configuration information. Even your documentation cannot live solely in your primary region. All of these things must be considered ahead of time and replicated to your DR region.