Your standard DVD will only hold 4.7Gb of data.
When I used to rely on CDs I would package my files into 'disc sized' folders and then move each folder onto a disc.
Done this way you only have one 'file' on the disc index and you can fill the disc. It is also easier to check for damaged or failed discs.
If you just transfer individual files each file name would be indexed and that can lead to a 'disc full', due to the disc index being full of file names, even though there is still space on the disc.
Now I just back up onto two external had drives, one weekly and the other monthly for archiving.
Extenal drives are fairly low cost now and much easier to back up then using DVDs.