Boot Camp Assistant Crashes after Initial "Continue"

christopher_AAPL wrote:

Snazzy Labs upgraded his 2017 iMac and talked about how he fusion drived his SSDs but warned it will reduce the life of the SSDs as they will constantly move files back and forth from now being fused. On other forums I've read people's experience where the NVME speeds will be lowered to the SATA speeds. Another person didn't experience that, but I imagine that is determined by which drive the fusion determines is the primary boot?

This is the 'down' side of Fusion with a secondary SSD. Fusion was specifically designed to move blocks from faster to slower storage to allow faster response from the most recently blocks used on a smaller storage unit.

I've gotten to a point where I've partitioned the 860, loaded a USB boot drive with Windows, began the process and formatted the partition to Windows NT File system, but when I select the now Windows-formatted partition, it gives the error "We couldn't create a new partition or locate an existing one. see the setup log files."

On this website https://www.easeus.com/partition-master/we-could-not-create-a-new-partition-or-locate-an-existing-one.html it says that problem occurs when another drive is connected, which I'm assuming could be my NVME but I can't remove that.

Yes, this is normal and expected and is due to the NVME.

Also, when I hold down option, shouldn't the 860 Evo come up as an option?

Only if an OS is installed. You have a NTFS File system, not a working Windows installation.

Also, now instead of Boot Camp Assistant giving me a crash report, it now just says "An internal error has occurred" when I click continue.

You have two APFS containers, which BC Assistant does not support and cannot handle.

If you have a Time Machine backup of your primary macOS installation, boot into Internet Recovery (Command+Opt+R), and then we can build your APFS Fusion drive, step by step.

See Posting Text Output in macOS Recovery Con… - Apple Community. This will help us coordinate as you perform each step.

You also wrote..

I have a iMac 2017 with Catalina (10.15). I recently upgraded my 1TB Fusion to a 1TB Samsung 860 Evo and 1TB NVME Samsung 970 Evo.

These two drives must be put back together as a Fusion drive, for BC Assistant to work, otherwise it will not start correctly. It is crashing because you have two APFS Containers, which BCA cannot handle.

christopher_AAPL wrote:

That’s very helpful, thank you.

NP.

I’ve read on other forums that it’s not helpful to apply fusion drive to two SSDs. Are there any drawbacks?

Can you post relevant link(s)? There are no drawbacks that I am aware of.

Typically, the larger of the SSDs is chosen for Windows. In your specific case, I recommend using the 860 EVO. Be aware that Samsung EVOs are problematic on Macs when installing Windows. macOS should work fine.

As a test, you can build the Fusion drive, as recommended, install Windows, and then remove Windows and split the Fusion drive. macOS can be run with the storage as two distinct drives.

If you must have Windows, and are willing to live with the performance of VMs, you can try VMware Fusion, Parallels or VirtualBox.

christopher_AAPL wrote:

One of the command lines is:

diskutil coreStorage createVolume FusionDrive jhfs+ “Macintosh HD” 100%

This is not valid for APFS Fusion drives. You will need to use

diskutil apfs createContainer -main <disk> [-secondary <disk>]
        where <disk> = MountPoint|DiskIdentifier|DeviceNode

Once the Container has been created, you can create individual volumes using

diskutil apfs addVolume <containerRefDisk> <fs> <name>
        [-passprompt | -passphrase <passphrase> | -stdinpassphrase]
        [-passphraseHint <passHint>]
        [-reserve <reserveSize>] [-quota <quotaSize>]
        [-role <roles>]
        [-nomount | -mountpoint <mountPoint>]
        where <containerRefDisk> = Container Reference DiskIdentifier
              <fs> = an APFS personality: e.g. "APFS"
              <name> = a volume name
              <passphrase> = optionally create an encrypted volume (disk user)
              <passHint> = some string that can be shown even while locked
              <reserveSize> = optional minimum guaranteed file data capacity
              <quotaSize> = optional maximum file data usage limit
              <roles> = one or more of 0|B|R|V|I; see changeVolumeRole
              <mountPoint> = "your" mount point (root only) (dir must exist)