All of my MacBook Pro 13" 2017 backups are kept on my Toshiba External HDD. I decided to update my MacBook to macOS Big Sur developer beta (because I am a dev) and test it out. I backed my MacBook up onto my external hard drive before installing macOS 11 Big Sur beta, expecting to be able to use it just in case I need to go back to macOS Catalina.
After I installed the beta:
Just about a half a week ago, after using the drive completely fine in macOS Big Sur, I plugged in my external hard drive and found that it did not appear on my desktop or in Finder. I opened Disk Utility to find that the disk was displayed as not mounted. I tried to click Mount, which was not greyed out, and I received an error that the disk could not be mounted:
Could not mount “TOSHIBA EXT”. (com.apple.DiskManagement.disenter error 0.)
I automatically assumed that this was just a bug in the new beta update and I reported it to Apple. However, I soon came to find out it was also happening on another MacBook Air that has macOS Catalina 10.14.2 installed. So it was obviously not the beta, it was the disk.
Why exactly did this happen on a disk that was working perfectly fine the day before? Was the disk affected by something in the macOS Big Sur beta or is it a completely unrelated issue? I was searching for solutions for this issue and found that it was somewhat common, and that people recommend using DiskWarrior to repair the disk, however, I cannot justify spending $100 to repair a disk when I might as well just buy a newer and faster SSD. Are there any other cheaper and even free solutions to this?
And in terms of data, I do not have data on the disk that is vital except for my MacBook Pro backups, which I was hoping to have on hand if something went wrong. If I bought a new drive, could I back up that from macOS Big Sur, erase Big Sur and install Catalina with the data from Big Sur?