Chapter 9 – Cloud Service DesignOnce you have installed and setup your management platform, we are ready to start with designing and delivering the cloud services using the platform.
SOA & CloudWe use the same principles of Service Oriented Modeling and Architecture (SOMA) that links business intent with its realization through IT for Cloud Services modeling as well. In SOA, we use the business process models to understand a series of sequentially organized business activities, events that trigger them, roles that perform them, inputs, outputs, control points, etc… As discussed in the Service Strategy section, we look to design the Cloud Services which are better aligned to business requirements
As in SOA, for service identification and design one could take any of the following approach.
- Meet in the Middle
In a top-down approach development generally usually starts with a high-level business and structural modeling of the service. Then you also define the management processes that are required service to be in operation. The top-down approach is further characterized in that no or only few automation or fulfillment assets exist when starting with the solution design. Design and implementation of those assets, including their interface and granularity, will be driven primarily from the high-level automation model. The advantage of the top-down approach is a clear design of the service to be automated, including the structural and operational model.
The bottom-up approach is usually characterized by a large number of automation assets that already exist. This may be in the form of many scripts or workflows already exists. In bottom-up approach, we take these low level assets and abstracting them as a cloud service.
Practically we might go with a combination of both approaches mentioned above as the meet-in-the-middle approach.
We model the service so we could learn, capture, and abstract details about “things,” their structures, relationships between them and, often, their behaviors (collaborations, states). All the factors that we consider during modeling a service in SOA are very much applicable for a cloud service too. These include but not limited to
- Service Portfolio ( in the case of cloud often referred as service catalog)
- Service Hierarchy
- Service Exposure
- Service Dependencies
- Service Composition
- Service NFRs
- Service Messages
- State management
- Realization Decisions.
The ABCs of Service Design for Clouds by David Linthicum is good article which discusses where SOA meets Cloud.
Service Management & Cloud
Now lets discuss the same from the Service Management / ITIL perspective. Cloud services have a lifecycle that maps to this service management lifecycle.
The Service Design phase includes the service definition, creation of the service and registering the same into a catalog. We will look at how these can be done using Tivoli Service Automation Manager in the next Chapter.
Service Design is a critical step that delivers the following benefits
- Faster service delivery with agreed and well understood qualities
- Business expenses follow level of value creation
- IT investments follow business demand and revenue generation.