Mapping of existing SSP in MOSS to Sevice Applications in SP2010

After the release of SP2010 there are lot of people are doing the upgrade from MOSS to SP2010. The MOSS FARM's use SSP which are no longer available in SP2010. Lot of people ask me what happens to the existing SSP which are there in the current SharePoint 2007 Farm. To answer this we need to understand the upgrade process in little bit depth. When the upgrade happens the installer creates 8 Service applications for each SSP in the current Farm before upgrading the individual Web Application. Here are the services which get created for each of the SSP in the Farm:

• Search Service
• Search Administration Web Service
• Business Data Connectivity
• Excel Calculation Services
• Application Registry
• State Service App
• Taxonomy
• User Profile

Following diagram explains this further and shows how the existing SSP are mapped to the Service Applications:

So as an example if we have 3 active Shared Service Providers (SSP) in the MOSS Farm these 3 SSP will be created as a bunch of service applications for each of SSP. So in essence we have 3*Service Applications which I have earlier mentioned.
Now the another interesting thing to understand is that when the installer does the upgrade for each of the Web Applications these service applications would be mapped to these Web applications. This mapping would be done based on which SSP earlier the Web Applications were associated and now corresponding Service Applications would be associated to the migrated Web Application.