Large store questions.

We are looking at doing a downloadable store with about 100K items on it. We had planned on trying to figure out how to call the downloadable content from a local server. Also I did read some threads on what people have experienced with over 50K items but I did not see much info on how people performed backups. Any suggestions or ideas?? Does anyone know the best way to setup the site for the downloadable content in regards to ordering?? I did see an extension with amazon's cloud but we need a DRM wrapper though.