Windows 10, Bootcamp, Logical Fusion Drives

"May 24, 2019 2:46 PM in response to Cory Schaal

• The W10 1809 (October) ISO contains install.wim which is larger than 4GB and does not fit a FAT32 partition.
• The W10 1803 (April) and older ISOs contain install.wim which is smaller than 4GB and does fit a FAT32 partition."

This info helps a lot, I knew there was a difference in images obviously, just didn't know what file was the culprit. I seen that apple suggested the earlier image for all installs, but this still doesn't work for me. When is apple going to allow BCA to create NTFS volumes? I mean really, we have native FAT support but not NTFS which is most common? :(

Loner T, have you had this happen? Have you gone through the steps on this exact model? I only ask because the 2017 model does not act like other iMac fusion drive models when it comes to partitioning/ using disk utility. You know that the only way to recover BCA broken free space is to break the fusion setup and format and reinstall Mojave right? It is not possible to do this through disk utility from the drive you startup from without a format. Period. Not Possible. Don't even try, it is not like a normal situation where you can + or - the drive partitions. You 'might' be able to break the fusion drive through internal recovery but I don't think it will let you as the drive includes recovery partitions. It may in some other circumstances or other models though.

I have tried Many ISO's as EFI and MBR installs and neither will work (I knew MBR wouldn't). I know that Mojave broke many BC partitions after the upgrade converted drives to APFS, apple states bootcamp will not work on fusions drives with APFS at all on (most) previous iMac models. Since I'm now about the 10th person (if not more) I see with this exact issue on this exact machine it would seem the system upgrade has issues like it has with other models, just a touch different.

I can guarantee the check disk command will return what everyone else's did so I won't bother you with that.

But to help others recover lost space after BCA breaks your setup here is what you do, keep in mind you will lose any and all data/ os installs on the drive:

First you Startup from EXTERNAL Mojave installer drive (hold option after making the drive at startup, this cannot be done with internal recovery), then open Disk Utility and format the "Container drive" that is holding your MacOS partition, this should then break the Fusion drive setup.

You will see something similar to this when the Fusion drive is separated. What you want to do now is format the SSD side and HDD side of the drive separately as Mac OS Extended/HFS+, I named them accordingly so they were easy to spot in Terminal diskutil list command.

Now Quit disk utility and open Terminal from the top menu. Once you are able to type you will want to see what disks and volumes are available (so you can create the fusion drive again). in Terminal use "diskutil list" without quotes and you will see something similar to the picture below. Note the section highlighted to show where the SSD and HDD drives are. You will see the HDD and SSD you just formatted.

In Terminal use the drive identifiers in the following command to recreate the fusion drive, here is my example:

diskutil cs create 'Macintosh HD' /dev/disk1s2 /dev/disk0s2

(where disk1s2 is the SSD and disk0s2 is the HDD)

This will recreate the Fusion drive but no volumes. Quit Terminal and go back into Disk Utility, You will see something like this

Now run first aid on the fusion drive and it will auto create your first volume

You can now Format the new volume as APFS or whichever you chose and rename it, then reinstall Mojave using the the normal method.

I hope this helps people recover lost space that cannot be given back through the OS. This was the ONLY way I was able to do it with this fusion drive. If someone else has a better way please let me know. I will no longer be trying to get windows in here natively as I am getting tired of rebuilding the drive and reinstalling Mojave. I was told going from Sierra/high Sierra to Mojave will not break the partitions but only remove the link for startup/shutdown options. I am not about to install those systems to find out if that is true though. Good Luck in the future, maybe apple will fix their mistake? Not sure why they released system that breaks a major feature that their customers rely on. Usually apple doesn't make these types of kiddy mistakes.

On another note, when I got the iMac I believe it came with Sierra, when I did a fresh install of Mojave I no longer had bluetooth hardware, and to this day no longer have bluetooth under system profiler or the system preferences. I was told by apple that its a faulty wireless card ($15 for OEM card on eBay) and that I was 4 days past apple care for the iMac and would have to pay a fee, he stated it would cost around $400 to fix. HA! I'll just remove the screen myself and replace the card and seal it back up for a total of $25 cost.

The strange part is that bluetooth was working in Sierra, but once I tried using a beats pill in Mojave I lost the hardware completely. Maybe I will go back to an older os to see if it comes back? Maybe my machine is truly faulty? Including the fusion drive? Hmmm....

I agree, it is a lot of work and becomes frustrating at each failed BCAssistant attempt, it is unfortunate that this was the only way to get the free space back since the BCA won't reassign it back to MacOS partition and Mojave disk utility won't let you modify partitions this way. I have even tried reformatting the BC partitions thinking BCA just didn't see them after failing, but even after a reformat and removal of the swap/installer partition BCA still wont allow you to reassign the free space. So to me this is an actual issue apple needs to address so people won't have to rebuild the fusion drive when BCA fails.

And as far as getting windows10 on a 2017 4k iMac with Fusion drive and OS Mojave... I'm not sure what to do other than go back to High Sierra and see if Mojave will break it after an upgrade. Nothing else seems to work.

So what is strange is that if I break the fusion drive, windows installer will see the SSD and HDD and install to either one just fine (obviously I don't want to do this), but once they are under Fusion setup as APFS the installer will not allow the bootcamp partition to be used, it will format it though, but then it just throws an error saying it cannot be used and to look at the log, which there isn't a log. Wish I could dig deeper and see what is really going on with the drive on the windows installer side.

You mean manually add a bootcamp fat guid partition under the fusion setup with disk utility? In its own container? or under the existing one for Mac HD? I am thinking something is screwy with UEFI section of the installer on the USB drive. Which I know in the past (on my 2011 iMac) was responsible for disk formatting issues through Windows installer using bootcamp. But making a hybrid mbr installer drive fixed it. Wonder is something like that is going on here? Just very strange, still waiting to hear that anyone was successful getting W10 on a 2017 Mojave iMac. Where is the evidence apple? lol

Edit: By the way, an interesting thing I noticed... it almost seems like BCA stops partitioning but really it did finish making the BC partitions, it just doesn't start copying the installer files to the OSXRESERVE partition, making me think its an image problem... I am going crazy enough to look into this, I will see if manually imaging the ISO to OSXRESERVE yields any results, good or bad.

BCA will not Restore free space/partitions after a failed attempt on this model, which is a big problem and why it needed to be rebuilt using external Mojave installer, you cannot delete partitions once they are made with Mojave, it just doesn't let you, even in restore mode. I'm not sure why it doesn't on Mojave, It may have to do with SIP not allowing drive changes to fusion APFS while in MacOS and even in Restore mode... That is just a guess though. When using Terminal/diskutil (from restore and inside MacOS) to remove the partitions they become free space, which cannot be reassigned to the MacOS partition through Terminal/diskutil. So far Apple's new file system is just causing problems no matter what way you look at it, which I guess I should have expected.

I am now having flashbacks of my early 90s pascal days and all the bugs present in OS 8 when we went from MFS to HFS and Extended volumes on non ppc machines, ahhhhh!!!

Yep, I was thinking that also, which is strange considering Apple has it's own NTFS file system driver for bootcamp support, I believe they had to make their own due to buss incompatibilities. Very interesting indeed. I did manage to find the older image, I'm just afraid that it won't work again, maybe I will create a 50gb partition and if its lost then leave it lost lol. My iMac (mid 2017) came with the last update of Sierra, maybe I will go back and just stay there until this gets figured out... or a different file system comes out haha.

Edit: Loner T, thanks for letting me pick your brain, it's great having someone to bounce off of, I appreciate all of your time taken :)