Modeling and Analysis of Availability for SaaS Multi-tenant Architecture

Software as a Service(SaaS) is increasingly becoming an important application development and delivery model. Among different implementation architectures, multi-tenant architecture(MTA) has received most attentions. Not only because it is easier to be maintained, but also increases the resource utilization. However, sharing the same instance will have impact on the availability of each tenant. Availability is a very critical attribute of tenants´ SLA, but modeling and analysis of availability for MTA SaaS is challenging. In this paper, we firstly discuss the differences of availability between one-tenant and multi-tenant from tenant´s view. Then we analyze the repair and failure rate based on the MTA feature and give the function expression with parameters of the number of tenant´s users. And a Markov model is built for availability analysis. We solve the model and get the computation expression of the availability in a case study. Then a numerical result is obtained under the specific conditions and finally we have a simply discussion on it.