For future reference of your burned (important) data, it might be handy to use a tool like DVDisaster (sourceforge).
In short, you have to sacrifice up to 20% of the storage capacity from the DVD. For a standard (re)writeable DVD this means that you can store more or less 4GByte of info. The rest of the capacity will be used to store data with which DVDisaster can recalculate your (important) data.
The software is available for Windows, Linux and Mac. What it also can do is checking the consistency of your disc and how fast your DVD player/burner can read the whole disc. When you download the software the online manual is included. My suggestion would be to check that one first to see if this software should be included in your backup strategy or not.
For me it looks like a nice little bit of extra data "insurance" without too much sacrifice (storage wise).
-Shades
I've been using this for some months now -- even got to test its recovery capabilities once
One caveat I've come across has to do with Bluray discs -- scanning seems to lead to the program dying if you're using the winPenPack portable version (0.72.2 rev 10 and 0.72.3 rev 10), at least with Windows 7. Otherwise it seems to work fine under Debian GNU/Linux as well as the setup-based Windows version (at least for some of the 0.72.x series).
For DVDs, I think I end up with less than 4 GB, but more than 3 GB to achieve the recommended 20% level of sacrificial space.
The main downsides seem to have to do with the amount of time it can take to generate the error correction data (perhaps my equipment is dated) and I haven't yet found a way to control it via the command line. It doesn't appear to support triple or quad layer Bluray discs yet, but I don't have access to such discs or hardware at this point anyway...
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