Like many of you, I was (and in some cases) was very confused about how SharePoint 2010 Search and the new FAST Search for SharePoint worked when the FAST product was installed in a SharePoint environment. My understanding was that when FAST was installed, SharePoint Search ceased to exist. Turns out – that was wrong. Let’s first take a look at a SharePoint Search only scenario:
So as you can see SharePoint Search indexed the content sources and the “people” directory to create a rich index and property database to be able to provide a rich Search experience. All of the goodness that has been added to Search in SharePoint 2010 is now available to the end user. While there has been a lot of enhancements to the new version of search, there still are some limitations that would drive someone to want to use FAST Search for SharePoint (more on that in another post).
So when FAST is added to the configuration, SharePoint Search is not removed from the configuration – they are actually sharing some of the roles. Take a look at this diagram:
Here you can see that SharePoint Search stays around to handle all search aspects of the People directory. FAST Search for SharePoint take point on indexing all all content. The secret sauce of providing a unified experience to the end user happens at the Query Object Model. It’s at this location where the 2 result sets are brought back together and ultimately delivered to the WFE and ultimately to the end user.
So there your go – when you use FAST Search for SharePoint – you are actually using 2 different search technologies.