Fix for Mojave Failure with Fusion Drive?

If you haven’t already solved this problem, this is what I had to do:

• boot the drive in target mode, connect it to a portable or other Mac running High Sierra (not Mojave);
• copy off all files
• reformat the SSD and HD as separate disks (if you reconstruct the drives as a fusion drive, all subsequent attempts to install High Sierra or Mojave will fail);
• disconnect, reboot the Mac in recovery mode (it will auto-boot in Network mode and collect the recovery software over the net);
• re-install the OS.

Was this a 3TB Fusion drive or was there a Boot Camp partition? I installed Mojave on two iMacs with Fusion drives without an issue. 2012 and 2015 27" iMacs, one with a 1TB drive and one with a 2TB drive.

I had the same issue with a 27" iMac 2015 with a 2 GB Fusion drive, and no Bootcamp.

So it's not only 3 GB drives.

Reverted to High Sierra from Time Machine, as many others. This was about a month ago.

I guess Mojave 10.14.1 does not solve the problem, or Apple would say so.

Same here. Upgraded to Mojave without any Problems and broke my Bootcamp. After Mojave update at the Release date there was just an bootcamp.dmg - image visible. No warning in the upgrade Progress, that this will happen. Please, Apple, implant Bootcamp again for Fusion drives... I am back now at High Sierra. Hope, there will be a solution for this.

I had been having major league fan problems for months, eventually locking up the iMac. So in desperation, I went and did a clean install of Mojave from a USB drive. All went well. Stupidly, I used migration assistant from my Time Machine backup. Then the fans started again. I know there's something in there corrupting the system, but can't find it using multiple methods.

So, I figured do it again, but this time, only bring back my known apps, not all of the historical garbage. Got to disk utility, and all was right until it gave me the spinning ball, leading to Drive Error. Now there is no addressable drive in my iMac, nothing. I can't get to it, even when booting from my CCC clone, it displays only the external drives, no internal.

Then I read up and find out just what is required to put a new SSD in the iMac, or even another 1 TB Fusion drive. OWC has a kit, and when I looked at the video, my stomach turned a bit LOL

Same here. Started around December and system got slower and slower. Now many corrupted unreadable files on my 3TB Fusion drive in Late 2014 Imac 5K. Booted up from external hard drive--trying to back up from 3TB fusion drive reveals nearly half my files unreadable.

Was working beautifully up until Mojave. Just 6 months past extended Apple warranty date.

Same problem here. My 3TB fusion drive on my 2014 Retina iMac is now completely corrupted. I can't boot the machine at all except to recovery mode. However it will not let me reformat the drive from Disk Utility so I can try and restore to one of my time machine backups prior to Mojave upgrade. Anybody have a solution? My Retina iMac is not currently useable.

I tried everything.... only thing possible was to reformat it using the instructions below...you're lucky you have a Time Machine backup...

Now it works well, but I haven't put more than 256 GB on there... I want to test what happens when I get out of the SSD part of the fusion drive.

https://www.tech-otaku.com/mac/secure-erasing-mac-fusion-drive/

Using the link in MS_MTL's post above I was able to reformat the fusion drive but it still did not work. So I uncoupled the fusion drive leaving two drives, in my case the 128GB Blade SSD and the 3TB HDD and was able to install Mojave on the 128GB SSD.

Now I see I am not alone with my iMac 2014 5K and 1TB fusion drive. After update to Mojave 10.14.3 system does 'work' but from time to time it fails to boot and I need to reinstall it from recovery mode... not very nice when you want to start your work in the morning and then you need to spend an hour for reinstalling system. Got iMac because of well know mac durability and quality (and payed for it quite at the time!) and now having problems like this... very sad... I hope they will do a fix for this

BINGO! Exact same f***ing THING! Late 2017 iMac 27" (without backup) and Mojave just crushed my Fusion drive. Made several attempts at saving it. Took it to Apple Store in Tysons Corner, VA. They were helpful, but ultimately couldn't do anything. Told to go to MicroCenter for a data recovery mission on hard drive. Mircocenter said those will run almost $1500!! I am stuck between wiping the drive and starting over (not happy) and searching for more answers before losing my data. An outrageous oversight by Apple.

I have a late 2014 27" iMac and have been putting off upgrading to Mojave because I keep hearing stories like this. I hoped Apple would have discovered the issue by now, but it seems like they haven't.

It does seem there is something up with 3TB Fusion drives.

I'm living this nightmare right now... it all started going to the dogs around Mojave time... on my 3TB Fusion drive.