HOW COMPONENT AVAILABILITY AFFECTS SERVICE AVAILABILITY
In order to understand the potential for the failure of an IT service, it is first necessary to identify the components or configuration items on which the service depends. Clearly, for the service to be available, all the components that contribute to the hosting and delivery of the service must be available. In a simple model where each component is connected in series (i.e. one behind the other), the availability of the service is the product of the availability of the components on which it runs.