Windows Server System Reference Architecture is a technology architecture that has been rigorously tested and proven in a partnered lab environment to provide exceptional planning and implementation guidance that addresses fundamental infrastructure issues such as availability, security, scalability, and manageability of the platform.
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http://www.microsoft.com/downloads/details.aspx?familyid=d44e34ec-b4e2-49a1-9f40-9ed4ba3765df&displaylang=en