problems with Fusion Drive

Good luck! 🙂

You need to boot your mac with USB installation thumb drive. After that;

Open Terminal

type

diskutil list

and press enter.

It will list your disks like this:

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *121.3 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_CoreStorage LogicVolGroup 121.0 GB disk0s2

3: Apple_Boot Boot OS X 134.2 MB disk0s3

/dev/disk1 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk1

1: EFI EFI 209.7 MB disk1s1

2: Apple_CoreStorage LogicVolGroup 999.3 GB disk1s2

3: Apple_Boot Recovery HD 650.0 MB disk1s3

drive1 is /dev/disk0 and drive2 is /dev/disk1 (as sample)

Type following command and press enter dont forget to change disk name (/dev/disk0 etc)

diskutil coreStorage create LogicalGroup /dev/disk0 /dev/disk1

When the process is done, your logical volume group should be completed You can find a unique identifier for the group, which you should copy to your clipboard. its starting wth UDID like this : 50B457C3-ADC6-4EDC-9ABA-FD8C6EEDE69A (change with your UDID)

Final command is:

diskutil coreStorage createVolume 50B457C3-ADC6-4EDC-9ABA-FD8C6EEDE69A jhfs+ "Macintosh HD" 100%

After that, you can fresh install macOS to newly created logical drive from USB or internet recovery. And restore from TimeMachine Backup.

Cheers

I recovered mine like this:

( ALL DATA WILL BE LOST! )

Start up in internet recovery mode with command-shift-R. Start the Terminal app from the utilities menu and paste in this line at the prompt:

( The following is all one line. Select all of it ! )

N=Macintosh\ HD; for d in /dev/disk?; do o=`diskutil info $d`; [[ ! "$SSD" ]] && grep -lqw 'APPLE SSD' <<< "$o" && SSD=$d; [[ ! "$HDD" ]] && grep -lqw 'APPLE HDD' <<< "$o" && HDD=$d; [[ "$SSD" && "$HDD" ]] && break; done; diskutil cs create "$N" $SSD $HDD && diskutil cs createLV "$N" jhfs+ "$N" 100%

Incidentally, I got this info from here:

https://discussions.apple.com/thread/7453778?start=0&tstart=0

Same problem with my 2tb 4k imac. Had to split my Fusion drive and then join them with above comands just to restore Sierra.