First I never would use a DVD writer for backups. I have two external HD (small and normal) with USB2 interface. The notebook type I use for moving data from one location to the other since it is not so fragile. In the worst case a flash drive would be the best solution. But why all this?

DVD writers are very slow. You have to write and you have to verify the data after writing. At a HD you can copy and even CHANGE the data at a very high speed.

The DATA amount on a DVD is limited. My big HD has 250 GB my small 80 GB - do this with DVDs...

DVDs you burn you should not mix up with what you can buy for instance as movies in a shop. They are stamped. What this means is that your burned DVDs are not accepted at all drives. For my Liteon 1693S I found so far only 1 brand/type my notebook drive can read - and I checked a lot. I found this brand/type by accident. Without it I would not be able to read my DVDs on my notebook. Any other media are useless for me. But my notebook is old. So more modern drives should do a better job. But this is not true for DL - here are still big problems for big money ;-) Even RW can be a problem if used on different drives.

For backup I would use HD drives. For distribution I would use normal burned CDs if possible. They are more widely accepted by drives than burned DVDs.