a new process under Msssearch.exe named Mssdmn.exe is spawned, and it is under this process that the content source is both enumerated and then crawled
In Search 2010, the number of crawl components across multiple servers can be increased as the workload increases, with automatic distribution of addresses, or if desired, specific addresses assigned to specific crawl components through Host Distribution Rules.
The current propagation information is stored in the Search_Service_Application database in the MSSPropagationTasks table, and the MSSPropagationLog table keeps records of past events and the query components populate the MSSPropagationTaskCompletions table in response. The MSSPropagationErrors table will reflect any current deficiency, and the information there is entered every 10 minutes in a warning level event on the search admin component’s server.
Since no single query component holds the complete index, the Query Processor service must manage disbursing the queries and processing the multiple results lists returned. This is accomplished, using a round-robin load-balanced method, by one of the servers running the Search Query and Site Settings service (an Internet Information Services [IIS] service).