Once the catalog is built, Search propagates the catalog to other Search servers. Search doesn't use Index Server itself, just its features. You can stop Index Server while building a catalog to reduce the requests the machine has to fulfill while building the catalog. A Key Concept File properties are key pieces of information such as the title, text, size, and date of a document. All files have similar properties, but properties are stored in different locations depending on the file type.
Some files have properties that only make sense for that file type.
An image document will have information about the compression type while Office and HTML documents do not need compression type properties. Index Server uses the IFilter interface to find those properties. IFilter is a specification for how to write filters and return file property information. Index Server chooses the IFilter to use based on the file's extension. Search lets you define what type of files to gather or ignore by the file extension as well.