FYI, MirrorDir does 1 file at a time, so you only need as much free space as the largest file you have.

The only downside to Roger's method is that it can't be used to 'keep' two empegs in sync without completely re-cloning. Mirrordir can incrementally copy over just the 'new' files. It does kinda need Linux to work well though - there doesn't appear to be a windows port. Although it *might* work in Cygwin, I haven't tested that.