I came across a great article on MSDN discussing various scaling options for SQL Server 2005, http://msdn.microsoft.com/en-us/library/aa479364.aspx. The article does a great job at relating data types and how they relate to scaling choices. The take away is that scaling choice is highly dependent on how the data is used by the application.
For more information regarding the Peer-to-Peer scheme, this article is also a great reference for some design considerations http://technet.microsoft.com/en-us/magazine/cc160974(TechNet.10).aspx.
Table 1. Factors influencing the selection of scaleout solutions
| Update Frequency | Ability to Change Application | Data Partitionability | Data Coupling |
Scalable Shared Databases | Read Only. | Little or no change required. | No requirement. | No requirement. |
Peer-to-Peer Replication | Read mostly, no conflicts. | Little or no change required. | No requirement. | No requirement. |
Linked Servers | Minimize cross-database updates. | Minor changes. | Not generally required. | Very important to have low coupling. |
Distributed Partitioned Views | Frequent updates OK. | Some changes may be required. | Very important. | Little impact. |
Data-Dependent Routing | Frequent updates OK. | Significant changes possible. | Very important. | Low coupling may help some applications. |
Service-Oriented Data Architecture | Frequent updates OK. | Extensive changes required. | Not generally required, unless combined with DDR. | Low coupling between services required. |