When you install Revit Server, you can store the central model of a workshared project on a server to improve performance for team members working across a WAN. When upgrading to Revit 2011 Subscription Advantage Pack or Revit 2012, you can migrate from the file-based system for storing the central model to the server-based system. For instructions, see Migrating a Central Model to a Revit Server in the Revit Administration Guide.