When Mojave came out a while back, I had attempted to update my 2012 27 iMac, but it wouldn't install due to a problem with the internal 1 GB Fusion drive. I checked it with Disk Utility (First Aid) and sure enough, there were lots of errors and it was unable to fix it, instead telling me to backup the drive and erase it. I was not aware of any problem and the iMac seems to work just fine, so I just kept trucking with it and bought a Samsung T5 to *eventually* back it up.
So yesterday I downloaded a security update for High Sierra from the App Store and it took FOREVER to install, restarting several times. I thought that maybe it had upgraded my Fusion drive to APFS, but it was still MacOS extended (journaled). So I ran First Aid in Disk Utility again, and to my surprise, the drive now checks out just fine with no problems! I went ahead and installed Mojave and that went off without a hitch. It even reformatted the drive with APFS.
Has this kind of situation ever happened to anybody else? I am relieved because now it doesn't look like I need to crack open this iMac after all.
Also, I finally downloaded Carbon Copy Cloner and made a cloned backup of my (now apparently fine) Fusion Drive onto a Samsung T5 SSD. It formatted it with Mac OS Extended (journaled), not APFS which I thought was odd. Disk Utility also doesn't give APFS as an option when formatting the T5 SSD either. The iMac boots up off the T5 just fine, but so far I am unable to see the T5 as an option in the Startup Disk control panel. I have to hold down the option key and manually select the T5 but it's just fine after that.
So yesterday I downloaded a security update for High Sierra from the App Store and it took FOREVER to install, restarting several times. I thought that maybe it had upgraded my Fusion drive to APFS, but it was still MacOS extended (journaled). So I ran First Aid in Disk Utility again, and to my surprise, the drive now checks out just fine with no problems! I went ahead and installed Mojave and that went off without a hitch. It even reformatted the drive with APFS.
Has this kind of situation ever happened to anybody else? I am relieved because now it doesn't look like I need to crack open this iMac after all.
Also, I finally downloaded Carbon Copy Cloner and made a cloned backup of my (now apparently fine) Fusion Drive onto a Samsung T5 SSD. It formatted it with Mac OS Extended (journaled), not APFS which I thought was odd. Disk Utility also doesn't give APFS as an option when formatting the T5 SSD either. The iMac boots up off the T5 just fine, but so far I am unable to see the T5 as an option in the Startup Disk control panel. I have to hold down the option key and manually select the T5 but it's just fine after that.