Availability Set vs Availability Zone vs Proximity Placement Group

Recently I have been working on a solution where specific application requirement sub-millisecond latency between tier workloads. At the same time, there has been a need for redundancy to ensure High Availability (HA) or Fail-over is being taken care of. Since Hyperscallers (AWS first to start then Azure followed recently and GCP had it natively and another cloud provider) has come up with Availability Zone (AZ) based (Software Define Networking (SDN) which connect different site within the same city or proximity) offering, solutions are being design taking it as defacto HADR solution.

While AZ is a cool feature and gives us flexibility and mitigate risk/cost of running parallel environment across different location, there are still some minor level things which are often being ignored. Some of those observations, I believe are following;

• AZ is never a native HADR solution, it is us who treat them as HADR
• AZ operate within the vicinity of city boundary (generally), which mean the environment is still exposed to a single point of failure.
• By Placing workload across AZ, we only add extra latency within the landscape because the request is hopping across different sites.
• Different Hyperscaller operates AZ differently, thus automation will be difficult to unify. Example: AWS AZ can be dictated by Subnet within VPC, GCP AZ can be dictated by Subnet but their VNET span across the region, Azure AZ cannot be dictated via Subnet within VNET.

Some test results and architecture pattern considerations i have tried to note down.

For more details, please have a look https://bit.ly/2TniNXR

https://cloudgyan.in/2020/02/27/availability-set-vs-availability-zone-vs-proximity-placement-group/

As i said always, i am not expert but more of learner. This is just small effort to spread knowledge.