Who may share with Whom?! Mixed-Tenancy: Conditional Sharing of Cloud Resources

Software-as-a-Service is a delivery model whose basic idea is to provide applications to the customer on demand over the Internet. SaaS thereby promotes multi-tenancy as a tool to exploit economies of scale. This means that a single application instance serves multiple customers. However, a major drawback of SaaS is the customers’ hesitation of sharing infrastructure, application code, or data with other tenants. This is due to the fact that one of the major threats of multi-tenancy is information disclosure due to a system malfunction, system error, or aggressive actions. So far the only approach in research to counteract on this hesitation has been to enhance the isolation between tenants using the same instance. Our approach (presented in earlier work) tackles this hesitation differently. It allows customers to choose if or even with whom they want to share the application. The approach enables the customer to define their constraints for individual application components and the underlying infrastructure. Based on these constraints, the SaaS application is deployment in the way that all constraints are satisfied and only minimal resources are required. This paper’s contribution is a summary of all results that were developed during the creation of the mixed-tenancy approach. These results focus on the challenges of capturing customers’ deployment constraints, computing a valid and optimal deployment, and an evaluation of the general applicability of mixed-tenancy in real-world.