diskutil list

Apple has an article How to fix a split Fusion Drive - Apple Support. I prefer to run the commands by hand to ensure there are no issues.

Restart the Mac, into Internet Recovery, and use the following steps as a reference. Once in Terminal, we need to erase both internal physical disks. Booting in Recovery can renumber disks, so we need to be careful on the next steps. If you run diskutil list, you will see two internal drives. One is your 28GB SSD part, the second is your 1TB HDD part. I will call the SSD as disk0, and HDD as disk1. If they are different, adjust the steps accordingly.

Steps should be

• Erase the SSD - diskutil eraseDisk jhfs+ SSD disk0
• Erase the HDD - diskutil eraseDisk jhfs+ HDD disk1
• Create the Fusion (CS) Volume Group - diskutil cs create macOS-LVG disk0s2 disk1s2 (please ensure the SSD is first).
• The previous step will output a long string similar to, which I will use as an example.

  F5D64E6C-7796-48E9-955E-46429D58A9BF

• Create the Fusion (CS) Volume - diskutil cs createVolume F5D64E6C-7796-48E9-955E-46429D58A9BF "Macintosh HD" 100% . The "100%" allocates the entire capacity of the two combined drives to "Macintosh HD".
• Post the output of diskutil cs list, before we start the restore.

We can address both issue in this discussion. Disabling SIP allows you to run commands, which otherwise are not allowed.

See About System Integrity Protection on your Mac - Apple Support for reference.

Reboot and hold Command+R, if you do not see a spinning globe or prompt for wireless password, you are in Local Recovery. Click on Utilities -> Terminal, and run

csrutil status

csrutil disable

csrutil status

If you see disabled, boot normally. This disables SIP. Once you problem is addressed, SIP needs to be re-enabled.

jeremylbt wrote:

I see. ok so after disenabling the SIP, I run the following command:

sudo gpt -vv -r show /dev/disk1

gpt show: /dev/disk0: mediasize=1000204886016; sectorsize=512; blocks=1953525168

gpt show: /dev/disk0: PMBR at sector 0

gpt show: /dev/disk0: Pri GPT at sector 1

gpt show: /dev/disk0: Sec GPT at sector 1953525167

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 1166729400 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

1167139040 786386095

1953525135 32 Sec GPT table

1953525167 1 Sec GPT header

This is your missing space.

For the missing disk space, should I run "diskutil eraseDisk disk1" to reformat the whole drive and reinstall Mac OS?

Please do not erase any disks. You will lose macOS, if you do. This can be corrected, if you boot into Internet Recovery. A reboot can renumber disks.

Click on Utilities -> Terminal, and run

diskutil list

and find the 1TB internal disk. Let us assume it is diskN, where N is a number.

You need to run

diskutil unmountDisk diskN

gpt add -i 3 -b 1167139040 -s 786386095 -t windows /dev/diskN

diskutil repairDisk diskN

gpt -vv -r show /dev/disk0

Select the entire session output, Copy (Command+C) it, quit Terminal, start Safari (Get Help Online), Paste (Command+V) the output as a reply to this discussion.

jeremylbt wrote:

I've executed your steps. I noticed there's a slight mistake in your last command:

diskutil cs createVolume F5D64E6C-7796-48E9-955E-46429D58A9BF "Macintosh HD" 100% should be

diskutil cs createVolume F5D64E6C-7796-48E9-955E-46429D58A9BF jhfs+ Macintosh\ HD 100%.

It should work both ways. Did you get an error with the first command syntax?

jeremylbt wrote:

The output of diskutil cs list is as follows: Should i proceed to do a TM restore on the Macintosh HD?

Yes. The CS LV/LVG look clean.

Do you see this

If not, reboot and check, otherwise run SMC Reset and check again.

You have a missing Recovery HD part on the HDD part of the Fusion drive. Can you post the output of

sudo gpt -vv -r show /dev/disk1

Do you see any error messages?