Cloud computing operational models
There are many paths to the cloud. Each path is grouped based on how the services are offered, deployed, and consumed. The cloud is not a technology. A cloud layer does not exist. Each path to the cloud is a response to a requirement or set of needs based on the consumer's current situation, desired future state, available skills, and resources, as well as tolerance for risk. Cloud products and services often establish reusable and reoccurring architectural patterns (building blocks) used for designing, building, and managing applications and infrastructure.
There are primarily three cloud service models: Internet-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS). Deployed as needed, all three models require network connections to change resource pools that are measured in great detail, dynamically. However, each consumption model differs in its approach to a technical solution, economics, complexity risk, and level of acceleration. Deployment models also differ in that they could be public/shared, private/dedicated, community, and hybrid. Each model is unique in how it addresses organizational risk tolerance, economic models, and management preferences.
Often the motivator for a move to the cloud is some event that triggers probing questions. Events could be anything from a magazine article, a blog post to a security breach, infrastructure downtime, a complaint about responsiveness, difficulty managing to the desired level of service, or staff/leadership change. Questions can be typically reduced down to three Es: Expectations, Economics, and Execution. As an example, someone expects more delivered work with smaller budgets and less time, or project execution unexpectedly fails due to budget and staff constraints.
As questions get asked, and solutions considered, strategy details, economics, and technology must align. Solutions that are technically perfect may be too expensive. Low-cost solutions may not match up to chosen strategies going forward. In all cases, economics need to balance or offset chosen risk level. For example, very inexpensive self-managed public cloud servers may not match up to the desired level of isolation and security required for transactional database servers.
Next we discuss ways to think through the three primary models available today. How do we recognize situations in which a cloud model should be a consideration? What are the characteristics of each model? What are the benefits? The following diagram is an overview of the three main service models:
