SQL virtual Hosting
This is a hardware-agnostic guide to building the infrastructure for hosting Microsoft® SQL Server® Database as a Service (DBaaS). By using the features of SQL Server 2012 and Hyper-V® virtual machines with Microsoft System Center 2012, a hosting service provider can start with very small tenant databases and scale out or scale up to meet the needs of the largest and busiest SQL Server applications. This reference architecture includes hardware, software, system design, and component configuration.
You can download Database as a Service Reference Architecture Guide here :