I would also recommend against compressing everything together into a single volume... especially when writing to optical disks. It's just far too likely that the media going bad (scratched, whatever) causes corruption somewhere - it's much better if that only prevents you from getting a couple of files back, rather than making it difficult to recover the entire compressed volume. I don't know how well tar deals with corruption in the middle of the archive. Maybe its really good, and my concern is unfounded, but I know my way works :) Plus, in practice, most of my big files that take up tons of space aren't compressable anyway.