I'm looking after an old Dell R450 that's being used as a domain controller and file server. It's running Debian/Etch (2.6.18 kernel). I stuck an LG DVD writer in it and have been using it for nightly backups to DVD-RAM disks (UDF file system). I've been doing that for about a year now and I'm starting to get errors on the DVD-RAM disks. I thought DVD-RAM would last longer than that but perhaps the people who change the disks aren't very careful with them.

It seems like it's only the odd sector here and there that is causing the problem. However, it also looks like the write operations keep using the bad sector time after time. Is there any way I can get the sectors flagged as bad?

Have you reformatted the disc? If that does not do then get a new DVD-RAM disc.
If you are relying on DVD-RAM as your backup it is best to have working media. Trying to bypass bad sectors, I would say more will develope.

Brian