my disk still not appearing in disk utility

Sometimes Apple's utilities get confused so try erasing the beginning of both the SSD and HD before trying to create the Fusion Drive again. To erase just the beginning of the drives use the following command, but make sure to replace "diskX" with the correct drive identifier. You need to use the command once on the SSD and once on the HD:

sudo  dd  if=/dev/zero   of=/dev/diskX  bs=100m  count=10

Sometimes destroying the partition tables this way will allow macOS to properly recreate a Fusion Drive. If you cannot recreate the Fusion Drive, then try using Disk Utility to erase the SSD, then erase the HD so they are separate storage volumes. If you get an error, then immediately try erasing the same drive again as I've seen the Disk Utility GUI fail for some unknown reason, yet succeed on the second attempt made immediately after the failure. This way you may be able to tell which drive is at fault (most likely the hard drive is failing).

If you have a full macOS external boot drive, then you can run DriveDx to check the health of the internal SSD and HD. Post the reports for each one here using the "Additional Text" icon which looks like a piece of paper. If you don't have a full macOS external boot drive, then I can provide instructions for creating and using a bootable Linux USB stick to check the health of the SSD and HD if you are interested. You could try running the Apple Diagnostics as well, but unfortunately the diagnostics don't catch most drive failures.

The "View" icon option only appears within Disk Utility for macOS 10.13+ although there should be a "View" menu on the menubar.

If you are booting into macOS 10.12 or earlier, then the default view already shows the physical drives on the left pane of Disk Utility. If the physical drive does not appear on the left pane of Disk Utility, then it usually means the drive has failed. In my screenshot the "Apple SSD AP0512Q Media" item is the physical drive. Of course older versions of Disk Utility will look a bit different than my screenshot which shows Disk Utility from Big Sur.

I used macOS earlier version. I have fusion drive. It is showing both SSD and HDD in disk utility. In about this Mac- Storage it only show HDD. When I am trying to create fusion drive looks SSD is unmounting and not processing further.

how to format SSD in fusion drive correctly?

I had this issue too. Followed Apple's directions to "Erase all in Group" PER THEIR INSTRUCTIONS and now it says start up disk can't be found. Help?

It's using the internet based start up and won't install OSX cause it says a drive can't be found.

aqueitstrength wrote:

I had this issue too. Followed Apple's directions to "Erase all in Group" PER THEIR INSTRUCTIONS and now it says start up disk can't be found. Help?

It's using the internet based start up and won't install OSX cause it says a drive can't be found.

Do you see the physical drive when you follow @BDAqua's suggestion above? If you don't see the physical drive, then it means the drive has failed. Or it may mean you are not booting macOS 10.13+ if you have a third party PCIe SSD installed or a bad SSD Adapter if you are using a third party M.2 SSD.

Are you doing this?

In the Disk Utility app  on your Mac, choose View > Show All Devices.

I did earlier and now also. It stopped on SSD (disk1) - error 69760 - Unable to write to the last block of the device

No view menu appearing in the disc utility to show all devices. Please help. It is using internet based startup after using erase option.

In Terminal…

diskutil resetFusion

Unable to write to the last block of the device

Gulp, in my experience I've found that to mean hardware failure, can you get an external drive & install to that?