A Method for Multilayer Computing of IT Services Availability

Today, one of the most important requirements for businesses is providing IT services with respect to high reliability and availability. This will enforce us to try to compute the availability of services and infrastructures with quantitative models precisely. Up to now, there have been many researches about calculating availability in IT services. However, most of them have concentrated on availability of computer and network modules. Some researches were interested in computing availability of a whole network additionally. But none of them paid any attention to computing availability of a business process from the user perspective. In this research, we provide a three-layer model for the overall availability modeling of a business process with respect to its underlying layers in an integrated manner. Then, we present some sort of formulas for computing service availability based on the provided model. This approach is responsible for assessing availability in large and complex networks with a unified measurement model between three layers consisting business, application and infrastructure layers. It will also lead both service providers and users to better and more exact perception of the availability of services, better management of QoS for service providers and better management of investments and budgets for users. The simulation results showed that losing a more important component will have meaningfully more negative impact on process availability than a less one.