Active-Active / Active-Stand-by architectural patterns are commonly used when we consider fail-over in server deployment design.
Active-Active
Following is the simple example for your better understanding of Active-Active Architecture.
You may have some question how to assign job at Load Balancer above. There will be following different approaches
- Round Robin (sometimes called "Next in Loop")
- Weighted Round Robin - as Round Robin, but some servers get a larger share of the overall traffic
- Random
- Source IP hash - if someone try DDoS attack from a same source IP, only the hashed server will be damaged
- URL hash
- Least connections, weighted least connections
- Least traffic
- Least latency
Active-Stand-by
This approach is super simple, but little bit wasting resources, so I usually don't like. By the way, Active-Stand-by is commonly used to build DR(Disaster Recovery) Center.
When you see, there are two different entities - one for Active, and the other for Stand-by. Stand-by means it does not work at all as long as Active has no problem.