how to upload files on scalable server clusters: a big production case

I'm making a species of file hosting website with node.js and xepler.

What I need is to understand how to handle a lot of files uploading (files sizes can be small as can be huge), without upload all the files users on the main server (where the main website is actually there), but scaling files on different clusters (or on a distribuite file system I don't know).. I need the technical know-how and the best approches that you recommend for this situation, so all yours advices, linking of guides, etc are appreciated.

Other infos: I upload the files client-side with HTML5 (ajax) and server-side using node-formidable

Thank you so much, guys!