How to create backups of DVD software discs?
A good way to back up of software CD/DVD install media is to create a disk image for each disk you want to back up, then you can store those disks images on a backup hard-drives, etc. The '.cdr' format is essentially a .iso which is the industry standard way of representing software disk images, so its a pretty good universal choice, that works on many platforms.

To create a disk image for an optical disk using the Disk Utility Application:


Open the Disk Utility Program
Insert the CD/DVD you want to create a disk image for.
Select the mounted CD/DVD disk under the "Super Drive" dive icon.
Click the Unmount button.
Select the the unmounted CD/DVD disk, by clicking once on it. 
Select "File" menu > "New" > Disk Image from  "YourCD/DVD Disk"
Set where you want to save the disk image and select Image Format: "DVD/CD master" plus any other options you would like, and the press "Save"