Service Applications are richer in terms of new features, scalability and flexibility. This is the logical container of the service, which is exposed through Managed Service Applications. It includes the management aspects of the service and configuration. When creating a Service application the associated databases and configuration will also be created.
A common question you may ask is why it is changed to be a service application in SharePoint 2010 with SSP. SSPs were pretty handy in Office SharePoint Server 2007. SSP helps to create a configuration of profiles, audiences, Excel Services, BDC and search that we could share between Web applications. If we wanted one Web application to simply use the same search configuration in one SSP but have a totally different profile / BDC configuration? The only option was to create a new SSP and target the search configuration. But these two SSPs were totally independent.
Services needed in web front end Servers
- SharePoint Foundation Web Application
- Inbound email
Services needed in App servers
You can decide which services should run in each app Server. But you should make sure SharePoint Foundation Web Application service should be stopped in App Server.
The Service Application Model also allows us to deploy more than one instance of the same Service Application. We can publish our service application into other farms. Simply install the service application's proxy in the other farm and point it to a specific URL provided by Central Administration when we publish the service application. This is a great feature that enables us to have dedicated service farms that can be specially configured based on the services that are provided. We can share these service offerings with other SharePoint farms or even with customer farms.