Victor Paraschiv's List: Scalability

out data that must be updated, but that still has a relatively low update
frequency, is often best handled by replication. Instead of several database
engines accessing a single copy of the database, you have multiple copies of the
database, so that each database engine maintains its own copy. This option
provides scaleout, while also allowing updates to the data. Replication is used
to propagate changes to all copies of the data. Figure 2 illustrates the use of
Peer-to-Peer replication as a scaleout solution.

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SQL Server Clustering on 2009-04-08