(09-02-2021, 09:55 AM)CyberMonkey Wrote: Would BIN/CUE or MDF be better than ISO at imaging physical SGI CDs and burning them back to blank media in that case?
First of all, once again, IRIX CDs are not ISOs, even if you name them *.iso. They do not have an ISO9660 filesystem, they have disklabel style partitioning and usually an EFS filesystem.
Some of the formats you mention are useful to capture 'special' discs, like CDs with copy protection mechanisms (games) or audio CDs. None of that is necessary for IRIX CDs. They are regular block devices. You can clone (image) them with dd.
The only reason to rename IRIX disc images to *.iso has nothing to do with IRIX, and everything with brain-dead CD writing software on Windows. It is fairly common that these programs will only let you choose from *.iso in their write disc image dialogs.
Regarding backups of IRIX discs (or optical media in common), there are two things to consider:
- Archival of discs (backup) to protect against damage or loss of the original and preservation for future users. For this purpose you want 1:1 copies of your originals. I had the 'pleasure' of working with a sysadmin in my university days who handed me a set of IRIX installation discs cloned with mkisofs .... not great for installation purposes.
- Derivative copies for ease of use or special purposes. Think of media for network installations (tar files). Because information gets lost in the creation of a derivative copy, it is not a replacement for a 1:1 backup copy. It is possible to create a TAR file from a disc image, but the opposite is very hard and will never result in a 1:1 copy of the original disc. Not all derivative copies need to be 'lossy': I have backups of my old IRIX QIC installation tapes. In order to use these for network installations you need to extract various files from the miniroot like sash and fx. But if I discard those and write the rest back to tape I have a 1:1 copy of the original tape again.
I have used the same methodology with my rather large collection of audio CDs. Initially, I simply ripped them into MP3s. This was in the days of the 486 computer, so disk space was precious and the process was tedious. I was roughly at the letter 'E' in my collection when I gave up. Maybe two years later I resumed, only to find out that I should have used something > 128kbit and that encoders had improved. I should really start all over again. Instead, I started to work my way back from 'Z'. Again, I didn't make it all the way through before I gave up. A couple of years later, I decided that if I was ever going to finish this, it would have to be the last time I ever did this. So I used ExactAudioCopy to backup all audio CDs to FLAC images with matching CUE sheets, log files and accuraterip files to prove the 100% correctness of the backup. I have created various derivative copies of my audio CD backups over the years: MP3's for in the car, M4A files for iTunes, iPods or iPhones etc etc. But (1) these 'convenience copies' are no replacement for the master backup copy, and (2) the idea was a success: I never had to pass my entire CD collection into a computer once more since. In the age of 10TB hard disks, space is no longer an argument either.
![[Image: collection.png]](https://jurassic.nl/images/collection.png)
