One key attribute of a cloud/infrastructure/enterprise architect is our ability to fully understand a customers requirements as it relates to Service Level Objectives (SLO) and Agreements (SLA). When embarking on a new architecture, understanding where the environment exists within the layers of the service offering and it’s criticality to other services built on it is critical. As you (the architect) work with your customer — engineering teams, application owners, other IT departments — it will be necessary to understand the interdependencies of all the services and how each services SLOs, RTOs and RPOs impact those dependent services.
The following diagram depicts the four tiers of service offerings and highlights the impact each tier has on a service offerings ability to provide a realistic and measurable SLO target.
The four tiers of services are:
- Foundational Services — The services contained within the Foundational Tier will be consumed by other services offerings either directly or indirectly. Examples include physical data center facilities, physical network service, etc.
- Abstraction Services – The services contained within the Services Abstraction Tier should provide a common API framework for integrating with the Foundational services. Examples include physical compute and storage infrastructure, cloud management layer (vRealize Automation, Kubernetes, Docker Swarm), etc.
- Consumer Services – The services contained within the Consumer Services Tier will be the first level of and most common services consumed by your customers if you are providing a software-as-a-service offering.
- Add-on Services – The services contained within the Add-on Services Tier are additional or complementary services that only function when combined from a service residing in the Consumer Services Tier.
As services are built, whether infrastructure or application, the impact they have on all other services increases as they move toward the Foundational Tier. Oftentimes our roles as architects will be focused on the Foundational and Abstraction Tier services. As a result, it is of the utmost importance to focus on resiliency and reliability for these tiers, as any outages or incident at these layers will be compounded as our customers build additional services which are reliant upon them.
From a VCDX certification perspective, it is important to be able to demonstrate your ability to understand and design around these interdependencies. I encourage all of us to further our understanding of the impact of our design choices to improve our skillset in the ever-evolving cloud technologies.