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Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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iMac SSD upgrade from Fusion drive, SSD seen as Fusion drive still?


I have upgraded 27” 2014 i7 iMac running a 1 TB Fusion drive to 1 TB SSD drive.

I have done many upgrades normally from standard SATA drive to SSD drive and works fine. After initialize new drive and format it in disk utility the SSD drive comes up as 1 drive.

However, in this upgrade, upgrading from Fusion to SSD I found that initialize went smooth and format also on another iMac but when I try to run disk utility to format it and install Mojave I see the 1TB SSD drive actually still as fusion drive.

A 1TB SSD drive should be as 1 drive but its actually coming up as 1TB SATA and 121.33 GB SSD.

It’s coming up as:

  • 121.33GB (disk0)
  • 1TB (disk1)

Would anyone one know how to fix this?

I have done in the past merging the 2 partitions on a 1TB SSD drive but it turned it into 1.12TB Fusion drive and I confused how it adds from nowhere the 121.33GB SSD component when in fact the SSD is only 1TB in capacity. Below is the instruction to fix a split fusion drive into one but is there a way to somehow remove the memory of the fusion drive on this particular iMac so it realises it now has a SSD drive as I am thinking that it’s got the memory of the old fusion drive details and not sure how to change?

Apple TN - How to fix a split Fusion Drive

I’ve also tested 2 other SSD drives (different brands/capacity) and the same thing is happening - they are appearing as 2 drives (split as fusion drive).

Update (07/02/2019)

The weird thing is I have tested a standard 1TB SATA (non-fusion) drive from another iMac and its also coming up as Fusion drive in the disk utility so it as if it doesn't matter what drive is tested it defaults to fusion drive based on the initial factory fitted drive it came with (very strange)?

I have reset NVRAM/PRAM and SMC and no success at all (thinking it would reset the chipset and register the new hard drive but it hasn't).

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my fusion drive will not work with a ssd in the place of a HDD .

the fusion only works with a sata platter drive. on my 27" imac late 13


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Solution retenue

It sounds like you didn’t split the Fusion Drive at the beginning. The Apple TN assumes you want to re-join the two drives into a Fusion Drive it fails to give you the commands to break it.

Here’s a good reference: How to split up a Fusion Drive This only works under High Sierra!

Mojave is different! Here we need to look within Terminal for the Fusion Drive container diskutil apfs list and then delete the container diskutil apfs deletecontainer diskX where X is container which states its the Fusion drive as an example Container disk2 - APFS Container Reference: disk2 (Fusion)

WARNING! Make sure you make a full backup of your drives and reformat them afterwards and install a fresh OS install of MacOS as you will loose the recovery partition.

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Hi Dan, I have tried to do this but no luck. As I pointed it out this is not Fusion/SSD drive but just a 1TB SSD drive. Splitting the drive doesn't make any sense since it's only just 1 SSD Drive (pls correct me if I'm wrong).

Trying to somehow get the iMac to realise its just one SSD drive as I've tested non-Fusion drives or other SSD drives and for some reason, in disk utility and terminal, it still shows as 2 drives which is impossible.


Lets roll the tape back here... The system was sold as a Fusion Drives system is that correct? If so then the system is still a Fusion Drive'd system in spirit at least ;-}

Which is why we need to break the Fusion Drive it still thinks it has. Ideally, I would like the system with its original drives installed and have the action done then so both the system and the drives are cleared of the interlink between them (HDD & SSD) and what the system thinks it has..


Hi Dan, yes spot on, so I'll put the original Fusion Drive in the iMac it came with and then through Terminal sort it out.

So as far as following the correct procedure if both the drives are APFS then I simply use this type of command ' diskutil apfs deletecontainer diskX ' or is there more to this process? Thanks Dan.


Thats it! You'll want to reformat the drives before you reuse them and the boot drive you'll want to do a full OS install.


I've removed the SSD drive from the 2014 27" iMac so there is no hard drive in it, went to disk utility from USB Mojave boot media and strangely there is still the SSD drive showing.


- 120.99 GB

- disk0s2

- Connection: PCI

- Partition no: 2

- Solid State: Yes

Wow, I thought that an iMac Fusion drive was as one hard drive. So it seems to me that the 2014 model 27" iMac (Fusion model) must have the 120GB SSD Fusion Drive component as a PCI drive and the 1TB hard drive is an additional SATA drive which would make sense.

Please correct me if I'm wrong, so now with the 1TB SSD drive added what would be needed is to merge them together as one drive which I would think.

Would this be correct and what about if the 1TB SSD drive was removed, would this pose a risk to the data written across both the physical drives and some of the system data would still sit on the PCI 120.99GB component?


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Howdy…I happened upon this thread as I have an iMac 17,1 (late 2015) with a fusion drive set up and I’ve been thinking of buying an upgrade kit, and a 4TB SSD with bracket to replace the 2tb spinny-noise making drive I currently have. It occurred to me that the upgrade videos that are out there don’t say anything about the original SSD that’s part of the iMac and I didn't realize (until this thread) that it’s a separate component which would still be there if I went through all the trouble ups upgrading the HHD to SSD.

Since I haven’t done or purchased anything yet, I’m wide open to what the best thing to do is to get a 4TB SSD inside my Mac…should I remove the HHD AND SSD? Should I “break” the connection of the 2, leave the SSD in and just replace the HHD with the new SSD?

Is using the SSD with an adapter bracket with a SATA sacrificing any SSD drive speed which wouldn’t be an issue if I removed the original fusion SSD and replace it with the 4TB SSD? Is that even possible?

Also, with enough training do you think we could get a cheetah and an elephant to have lunch together?

Thanks in advance!

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I still like HDD's! The issue is what your intent is... If you are looking for speed then I would replace the PCIe/NVMe blade drive getting at least a 500 GB or if you can swing it a 1 TB. Then after breaking the Fusion Drive set setup the blade SSD as your boot drive with your apps. leave the rest of the drive empty. Then use your HDD as your data drive holding your stuff. If that is on the small size then upgrade it to a SSHD (hybrid drive) like a Seagate FireCuda.

Here's more on the custom Apple SSD's The Ultimate Guide to Apple’s Proprietary SSDs


This isn't an answer - it's just another question!


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Adrian sera éternellement reconnaissant.
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