By definition, a virtual search server is a collection of one or more indexes and their related configuration files. Indexes are at the heart of a virtual search server. An index is an optimized binary file that contains keywords found in documents hosted on a Web or file server. Indexes are used by Web Search to return search results to users' Web browsers.
Before creating virtual search servers, particularly large or mission-critical ones, you should carefully plan how to configure your search services. A virtual search server that will be used by a small to medium department in a company requires different planning than a search server that will serve thousands of customers on an Internet site.
For information about how to plan an effective search service, see Designing Your Search Solution.