Allow indexing of content outside of Confluence

We have a large amount of content that we would like to put into Confluence, but we are worried about the amount of space it will take and the additional size of the backups.

If we could store the files in a directory that:
a) Confluence can see locally (maybe within the confluence directories)
b) Can be accessed via a URL (maybe manual setup within Tomcat)

If the indexer could also look at these directories we can find these URLs easily.

If you could even index external sites that might be useful (although potentially time and space consuming).