Was just reading the new downloadable book: Administering Enterprise Search for Office SharePoint Server and ran across some metrics that I was unaware of before today.  When you setup your SSP SharePoint asks you about the indexer performance settings, which are Reduced, Partially Reduced and Maximum.  Up until now, I didn’t understand the “magic” behind these settings, but the following table explains it in fine detail:

The maximum setting did shock me a bit when throwing real numbers at it.  Say you have 8 processors in your box and you have search set to maximum (because you just want to get to get it over with as soon as possible) that means that you would think you could have 128 threads available for crawling.  It however looks like the number of threads are capped at 64 regardless of your crawler impact rules or number of processors (good to know when ordering hardware if you are going to have a dedicated index box).  With actual numbers like that, just remember what that could do to the load on your servers and to your network.

["Brian"]