I do the same but now i can't create a new Fusion drive. And can't even reformat Apple SSD ( 24Go) PCI Express in HFS....
I can only install OSX on the other drive. The PCI Express card is for moment lost in the Darkness of this New APFS systhem. I format cause OSX 10.13 can't be installed in APFS format grom my previous instalation.
It's only 24Go lost but PCI Express was a good point for fast runnig OSX....
I will try without this PCI Card for moment ...
I will check when Apple give us a solution to resolve this problem and when we can agin created a FD with Terminal between this 2 drive in APFS
It is possible yes, I managed to format my fusion drive to APFS as follows via the command line:
diskutil apfs createContainer disk0 disk1
diskutil apfs addVolume disk3 APFS “Macintosh HD”
Once you complete the second command the 2 drives are replaced with the Fusion Drive when viewed in Disk Utility.
Your disk references might be different depending on you config.
I am going to try this.
I reformatted my MBP fine APFS and installed 10.13. So I thought I would give the imac a try…
My first attempt split my iMac late 2014 1TB fusion drive. I reconnected it in terminal and reformatted as journaled and reinstalled 10.13.
But the iMac seems slugish and takes longer to reboot. I was wondering if the OS got installed onto the SSD part of the drive? Is there a way to check? Or to manuall select the SSD as installation of the OS?
Then I will try your command line and try to reformat to APFS
Can you please explain the procedure from the start? Here in India even Apple support is unable to help me.