I was just supposing. Say you have a large file split across n DVD backup discs, and one DVD becomes unreadable (gets scratched or something).

Is there a way to write parity information to a series of DVDs such that if you lose one, you can recover the data from the others? Of course, as most people only have one or two DVD drives, this information would have to be read in serial.

Basically, I am wondering if there is a way to write out RAID5 data/parity sets onto DVD rom drives?

Obviously there are better backup methods - this is a hypothetical question to gain insight. Any ideas on how to procede with this?

You certainly can create RAID5/6 data parity sets. Simply setup a software RAID5/6 using files (each smaller than 4.4GB) which are loopback mounted. Once the array is populated with the data you want, burn the individual files to DVD.

However, you may also want to look at "file RAID", as is provided by utilities like rar and par2.