Zero Outage Layered Model
As the Zero Outage Industry Standard strives to achieve Zero Business Outages it has to be applicable to a variety of IT Environments. In today’s world where business value is created by integrating various systems often across company boundaries, it is crucial to look at Systems of Systems. Complex combinations of on premise data center solutions can work hand in hand with cloud solutions and even further with non-data center IT like Internet of Things devices. To bring architectural clarity, the Zero Outage Industry Standard follows a layered model. This model takes into account the way IT is deployed in terms of shared versus dedicated usage and traditional versus cloud implementation.
As depicted in Figure 1 there are three horizontal layers. The foundation is called Basic IT Infrastructure, containing everything from data center facility, cabling, compute, network and storage capacity. On top of this basic layer follows the IT Services and Applications layer where software using the underlying IT Infrastructure exposes IT functionality to other programs or to humans. Both before mentioned layers together then build the foundation for the Business Solutions layer above. A business solution may offer functionality as required by one or many business processes. A more detailed view of the three layers will be covered in the platform section of the Zero Outage Industry Standard.
Remark: In future publications the Zero Outage Industry Standard may also include IT equipment that resides outside of data center environments. Examples might comprise departmental IT equipment, mobile devices or Internet of Things devices.
Depending on the actual implementation each layer can be used by one dedicated client, by a small number of clients that share the resources of that layer or by a large number of clients. Dedicated is most owned and operated within the traditional enterprise data center environment. But also IT Service Providers offer dedicated environments in an outsourcing type of service. Shared environments span a wide range of implementations from company internal solutions to cloud services. Public is generally offered as cloud solution to provide the scale needed to support a massive number of users.
Within the previously mentioned layers, a set of functionalities is exposed by building blocks. Those building blocks are a group of components that provide a specific functionality. Components are then realized with concrete products.
From a business perspective every solution can be created from combination of building blocks or components from all layers and across the various deployment models. It is very seldom today to have a solution where a straight line can be drawn from the desired business outcome or functionality to an individual IT Service or Application that uses a single stack of IT infrastructure. The norm is rather to have a number of IT Services, Applications and infrastructure elements that have to work together to provide value to the business. Figure 2 shows an example of a business solution that leverages a number of building blocks dispersed across layers and deployment models.
To make sure that the goal of Zero Business Outages is achieved, every building block has to provide the appropriate level of resilience, depending on the capabilities of its components and the capabilities of other building blocks. It might be possible to raise the capabilities of one building block and therefore to lower them on another one or the other way around.
One example could be to use multiple components with almost no build-in resilience and use some intelligence on a higher level to achieve the desired resilience by orchestrating them. Following that principle of delegating functionality (in terms of resiliency) to higher levels would offer some freedom in the way a solution is implemented and allows to find the optimal balance between resiliency requirements and affordable cost per component.
To enable the principle mentioned above, it is necessary for each component or building block to offer the following:
- It must not contain nor be a single point of failure itself,
- it either has to fulfill the Zero Outage Industry Standard criteria for that kind of component or, if it does not fulfill the defined criteria, it has to define what it requires from a higher layer.
Figure 3 depicts an example.
At the center of the above picture is the component of a building block. On the left is an example of the list of ZO requirements (coming from the ZO Platform Design Principles [future release] in that case) and on the right it would provide a definition of requirements to other components within the same or in higher layers.
The Layer Model provides an overview to allow individuals or companies interested in the Zero Outage Industry Standard to easily understand some basic concepts and ideas. Together with the Zero Outage Map it offers overarching design principles, which are further detailed out in the documentation of the work streams that cover people, processes, platform and security.