I'm also intrigued by the idea... there's a few barriers in the way first though.
It's not possible with current software / EvoX. First, EvoX only opens up an ftp *server*, it doesn't know how to be a client. Also, it only allows one connection, so using an xbox as a cluster or as a server for other xboxes is out of the question, at least for now.
Other issues: xbox doesn't take "drivers" like a PC, the only drivers are for the dvd and hdd, and they are located in the bios and hard-allocated to the specific ide channels... so, even if you could point it to a networked ftp connection, it wouldn't be able to recognize it as a readable IDE drive. **not to mention the formatting**. There are many barriers in the way of this project, but I would personally expect all of them to crumble within the next 6 months, especially when we get our LinuXBOXes.
I'll be trying to write my own solution for it in the mean-time, but I'll need a bios update before it can take off.
peace.
