DONT GET DVD+RW DISCS, THEY ARE NOT GOOD FOR BACKUP
GET DVD+R DISCS
DVD+RW are re-writeable and files on there can be deleted, this is NOT good for backups.
DVD+R are write once, never delete. This is far more sensible for backup as once the data is on the DVD it cannot be deleted.
You may think that you will never delete anything off a DVD+RW but it can easily happen, by accident for example.
If your drive can support DVD+RW it can also support DVD+R.
So for backups use DVD+R discs.