Today I offer a technique rather than the traditional Q&A. It works this way:
I have a double-layer installer disc that I wanted to back up to writable DVD media. Although I have a Mac Pro, which is capable of burning DL media, I didn’t have any DL media on hand. What to do?
Ah, I have a copy of Roxio’s $100 Toast Titanium 8 on hand, which supports disc spanning—a feature that allows you to write one or more files across multiple discs. All I need do is convert that DL disc to a single file that can be split between two regular DVD-R discs.
I did this by launching Disk Utility, choosing File -> New Image From Folder, and, in the Open dialog box, navigating to the DVD, selecting the DVD, and clicking Image. In the New Image From Folder window I chose DVD/CD Master, left the Encryption pop-up menu at None, and clicked Save to create the image.
Once the image was created, I launched Toast Titanium 8, chose the Data heading, and made sure Mac Only was highlighted. I then dragged the disk image I created from the DL disc into Toast’s main window. From the media type pop-up at the bottom of the window (the small pop-up that appears next to the big Record button in the lower-right corner) I chose DVD. The Options area of Toast told me that the image would span two DVDs. I inserted a blank DVD and clicked the Record button. After many minutes, Toast ejected the first disc and asked for the second (it verified the recording of each disc).
The first disc in the set included a copy of Roxio Restore, the application placed on a spanned disc set by Toast. To restore the image to my computer I simply launched Roxio Restore from the first disc, selected the image that appeared in the list of files, and clicked Restore. The program went about its business, first copying data from the first disc and then asking for the second disc to complete its job.
Eventually I had the disc image back on my computer. Double-clicking it mounted a volume identical to the original installer disc. Double-click the installer and I was good to go.