27" 2019 iMac, Replaced HDD with SSD, Can No Longer Install Windows with Boot Camp

Question

Level 1

8 points

27" 2019 iMac, Replaced HDD with SSD, Can No Longer Install Windows with Boot Camp

Hi there,

I have installed a new SATA SSD to speed up my iMac (500 MB/s versus 100 MB/s) and I've been having troubles running Boot Camp Assistant. (I also replaced my NVMe SSD, as an FYI.)

It always stops me with,

"Boot Camp Assistant has encountered a problem

An internal error has occurred."

I've read from numerous other posts that this is because it requires a Fusion drive, by others seem to be fine with an SSD install... maybe because they got a machine with Fusion drive? Not sure.

Anyway, I thought I would make my own NTFS "Windows" drive from my SATA SSD,

But I ended up erasing it and giving it back to my SATA SSD after it didn't work. I'm sure it has something to do with the GUID / MBR.

Anyway, here is my current (and original after install) disk layout,

diskutil list

diskutil apfs list

Is it possible, whatsoever, to have Boot Camp recognize my internal SATA SSD (/Volumes/Internal Storage) to install Windows? Or is there any setup / partition change I can do using my setup?

Thank you so much!

iMac 27″, macOS 10.15

Posted on Aug 10, 2020 7:37 PM

Reply

Answer 1

Top-ranking reply

Loner T

Level 9

59,513 points

Aug 11, 2020 8:01 AM in response to brettalton

You need to rebuild the Fusion drive. Your internal physical disks - disk0 and disk1 - are in different APFS Containers.

Create a Time Machine backup of macOS
Repair the Split Fusion drive - How to fix a split Fusion Drive - Apple Support.
The Fusion drive can also be manually rebuilt, if necessary.

Reply

Answer 2

brettalton Author

Level 1

8 points

Aug 11, 2020 10:45 AM in response to Loner T

Hey this is fantastic Loner T, thank you so much for the direct help on my specific use.

I have no problem running that command after my Time Machine completes. However I do have a question.

I ran the command and this is the output,

diskutil resetFusion

However, it has my disks incorrectly listed as bigger/faster.

disk1 is the slower drive (SATA SSD), so should be used as the "secondary" drive

disk0 is the faster drive (NVMe SSD), so should be used as the "main" drive

I looked at the man page for diskutil and couldn't find anything to force this manually,

man diskutil

Would you be able to help me here, setting disk0 as "main" and disk1 as "secondary"? I'm almost there!

Thanks!

Reply

Answer 3

brettalton Author

Level 1

8 points

Aug 11, 2020 9:43 PM in response to brettalton

Just a follow up... it seems because the NVMe drive is over-provisioned, APFS/CoreStorage think it’s the “secondary, designated aux use” drive. This simply will not sure and the reason why I cannot run `diskutil createFusion`. It selects the wrong device for “main” versus “secondary”.

I’ve looked at as many man pages as I can and creating a container and volume using these disks and the cs/jhfs+ or apfs/apfs method will not allow me to select which drive is which.

Is this possible?

Reply

Answer 4

brettalton Author

Level 1

8 points

Aug 11, 2020 9:52 PM in response to brettalton

Well I finally found it... and it looks like it’s telling me I’m “trying to make an upside down container” where one disk, Main tier, is larger than the other disk, Tier2. Is there any workaround on this?

Reply

Answer 5

Loner T

Level 9

59,513 points

Aug 11, 2020 9:55 PM in response to brettalton

Yes. You can specify which disk should be main and secondary. See the -main and -secondary qualifiers

diskutil apfs createContainer
Usage:  diskutil apfs createContainer <disk> [<disk>]
        diskutil apfs createContainer -main <disk> [-secondary <disk>]
        where <disk> = MountPoint|DiskIdentifier|DeviceNode
Create an empty APFS Container. You can then add APFS Volumes with the
diskutil apfs addVolume verb. If you specify two disks, then a "Fusion"
Container is created, with the performance usages assigned automatically
unless you use the -main and -secondary options, in which case, the secondary
disk is assumed to be on "slower" hardware. The secondary disk is often used
to store associated "auxiliary" data, such as a Boot Camp Assistant partition.
Ownership of any affected disks is required.
Example:  diskutil apfs createContainer disk0s2

Reply

Answer 6

Loner T

Level 9

59,513 points

Aug 11, 2020 9:57 PM in response to brettalton

Try using the -force qualifier.

Reply

27" 2019 iMac, Replaced HDD with SSD, Can No Longer Install Windows with Boot Camp

Similar questions