Putting a DVD writer in the server is the easy part. I have put three different ones in an they have all worked fine. The hard part is using is to do backups, which must must be the only reason to put on in the system.
See this thread:
http://forums.contribs.org/index.php?topic=19413.0I started this one months ago, and still have no answer that actually works. You can use tar, gzip, mkisofs, and cdrecord to burn a backup image of specified directories to a disk, but if the the tar file is over 2 gigs, then I have yet to figure it out. There was an offer from someone in that thread to write a how-to, but nothing ever came of it. I am still pretty desperate to find a real solution.