I am in a no win predicament. A week ago I was booting from an older external HD in order to copy some email info off and a number of other perhaps semi important things off before reformatting and getting the drive wiped foe later use. Well, I was getting data of fine have to step away for the evening, next day when I tried to wake my Mac Mini up and continue, it wouldn't. Screens were black, caps lock works so the system was still "up" but it did not seem to wake up. Have had this experience a few times over the years and simply powering the computer off/on would resolve the glitch. This time it did not. System came up from the original boot disk and the external drive I was booting from did not show up. A dive into Apple Disk Utility for a fix seemed in order. Inside Disk Utility I see the drive but not the partitions I expected to see. There was 3 partitions on the drive and it seemed to pick up one and a grey'd out APFS Physical Store disk7s2. Any attempt to "repair" this disk fails. "Storage system check exit code is 8." "Storage system verify or repair failed.
-69716) Tried doing a FSCK, FSCK_APFS and so on with no luck. Tried other disk utilities, Dirk Warrior, Disk Drill, TechTool Pro 7 (older version) and not one would see/fix the drive. I resorted to a web search which brings me to this site. Tried TestDisk and it looked promising in that it showed 4 partitions of different sizes. I was hoping to restore the drive but there is a lot of information I think you need to accomplish this. I think you need to know all the partition details so if you need to input them again and save the info to hopefully get the device back. This I did not have at hand. Also, FDISK seemed to give different results in comparison to TestDisk. So, I do think I an pooched unless someone is more familiar with this APFS recovery process. Apple forums simply say good luck! Now, there could be an issue with the drive that is unrecoverable so I might be batting my head against a wall anyway. I am at this point not expecting a fix. I did get some data back in many different recovery folders which I would now need to go through and sort out the stuff I would like to keep. I would add some screen shots but it looks like they need to be linked to a web site to link them. Too many jpgs means the system requirements are to high - I understand that. In a perfect world I would be able to restore the drive to a bootable system and grab all I needed off properly, however, I think what I have is about as good as I can get. If there is any suggestions, I am up to playing with the drive at this point and not expecting much. There is dramatically more to this than I was ever aware! LeSigh.
Bill