All of those things seem like they would be true. But even on a very basic implementation you shouldn't have to hit the disk all that often unless you have an

All of those things seem like they would be true. But even on a very basic implementation you shouldn't have to hit the disk all that often unless you have an extremely large number of static files to serve. This is quite possibly the case for many sites, but I think for most sites, all of your static files could be cached with a minimal memory hit.