OS X Upgrade to Catalina - Disk Utility - Fusion - Terminal - Expertise PLZ
First the history: 5 years ago I bought 2 identical Late 2012 Mac mini 6,2 i7 2.3 w/1TB HDD (not Fusion) w/4GB RAM that I upgraded with 256GB Samsung SSD in Bottom Slot/Boot position and 16GB RAM, moving the HDD into the top slot/non-boot drive position as directed by Apple guidance.
After a past iMac crash issue opted to leave Mavericks installed on the HDD (to run utilities on the SDD or SSD crash recovery rather than wiping it) but use it for general storage of files, downloads, etc.
I formatted the SSD with DU and installed Yosemite then later El Capitan which worked great and was lightning fast booting/launching applications. All was fine until Dec 2019 when Safari started dragging and I found adware (scrlink.cool) which I resolved, but Safari still struggled, so I reinstalled El Capitan.
That was a disaster; OS installer merged both drives into a Fusion config that Disk Utility couldn't Undo rendering the SSD useless. It had somehow installed Yosemite on the HDD and despite countless hours trying to repair or update or recover the previous image and config from Time Capsule, it's been futile.
DU tests report that both drives were fine but I always get a message that 'Update Cannot be Installed', no matter what was tried. Subsequently, after running DU and the OS X Recovery numerous times both drives disappeared and wouldn't mount which left me staring at an empty black screen.
Present issue: I tore down the Mac mini and removed the SSD attached a USB/SATA cable and plugged it into my MB Air which allowed trying to install OS X but despite DU reporting it as perfect, absolutely no approach worked regardless the OS X version. BTW - DU Info reported it as an external volume.
So I wiped it, reformatted as Journal Ext/GUID and with a clean slate tried installing OS X at which time reported ... yet again... the OS could not be installed - I presume because it still thinks it's a Fusion drive.
At which point reassembled the mini exactly the same as before, booted to find neither drive mounted so ran DW - BTW OS X Online Recovery tools were essentially useless - which found/mounted the HDD but not the SSD, maybe because it was formatted on a USB bus? Then I tried (unsuccessfully) for 2 days, hours on end, of downloads and attempts to install/update any version of Mac OS X on the HDD.
So, having nothing to lose, wiped the HDD and reformatted it trying again to install OS X at which point it indicated it qualified to have Mavericks installed!? I just cannot fathom why it took so many hours and tries over one year for Apple to FINALLY disclose that Mavericks was the ONLY OS X that could be installed!?
Voila, after all the wasted time and frustration, Mavericks did install and booted: it looks just like 2015!
Thinking all is well, opened the App Store, downloaded Yosemite again to begin the updating route to Catalina. Wrong! After three 2 hour installation attempts, all of which get to finalizing, reports the mini doesn't qualify for OS X. Why doesn't Apple know that BEFORE jacking around and wasting a user's time?!
Before taking a hammer to it I decided to try installing Yosemite from the DVD one more time... guess what? This time, after abundant whirring and stepping sounds it - for no apparent reason successfully installed Yosemite which launches and seems to operate normally.
After which I again downloaded El Capitan from the App Store (purchases) and discovered it will not install either!!! Really?!! What the **** is going on with these obtuse Mac OS installation packages? At this juncture my Mac mini is back at the exact point it was 5 years ago. At least it works, albeit paralyzed.
But Disk Utility still doesn't see the SSD, nor does Disk Warrior. Is there a set of Terminal commands to access the system to see what is connected to the bus and change/correct pertinent logical attributes of those devices? I suspect that the SSD, having been reported as an External Device on the MB Air DU, has been formatted logically as an external drive and the Mac mini can't see it on the motherboard bus.
BTW: The other identically configured Mac mini is still fully functional, racing along with Mojave OS on the SSD with the factory installed 1TB mechanical HDD used solely as a storage volume. What gives?
I'll be deeply grateful of someone can, please, advise me on how I may proceed to resolve and correct this set of maddening issues. I desperately need to get this Mac fully operational and put back to work.
Thank you, in advance, for any constructive assistance and instruction you may render.
Best regards for a productive 2021.
Mac mini, OS X 10.10