Test-Drive SQL Server Data Services: Figure 1 Layered Architecture Is Highly Scalable.
SQL Server Data Services (SSDS) persists flexible Entity sets in specially customized, clustered SQL Server 2008 instances running under Windows Server 2008 on commodity servers in Microsoft's domestic and overseas data centers. The term flexible applies because an Entity consists of a combination of metadata properties with a property bag of up to 30,000 named entity/value pairs. Containers store one or more Entity sets and are the basic unit of data consistency and the boundary for queries. Authorities present a specific service URL and billing entity for a group of Containers within a single data center. The "head" is the Web-facing interface to REST, SOAP, and Sync Services clients and middle-tier components.