Just one quick note - a summary index is an index. You can set up one, or hundreds, depending on your use case. Generally, most places I've seen will keep their summary indexes pretty locked up to one subject per index. It's not always only one record type, but you wouldn't usually be mixing, say, summary statistics about your employee work and pay in the same index that you are summarizing hits on your web pages, and those wouldn't be together with your sports stats, or your summaries of employee logons to hosts. This is partly because of access controls, but it's also because there's nothing to be gained by throwing all the stuff together.
