General Backup & Archive server

We're looking for proper storage for an incremental backup server off the hard disks used for daily work (our home directories), and a way to put the more stable data on DVD. Our current file-server is already very secure against failure (it has 8 disks, organized in pairs, and we can lose one disk from every pair before losing real data), but it's preferable to have some way to put the user's data on removable, non-erasable media.