De- Fusion a fusion drive in iMac ? using only SSD

[kenfused]

My 2019 iMac is slow recently and DriveDx says the mechanical SATA is failing on the fusion drive.
I'm planning to transfer everything to an external SSD 2TB, and for now boot off the external SSD and make sure everything works ok. and I was wondering if I can easily "de-fusion" the built in drive, then using the 512 SSD inside the imac as the boot drive, holding only the OS and maybe Apps, then putting all the data on the external SSD.

(I dont want to open up the iMac)

Any tips/hints on how best to do this?
Thanks!

 

[DeltaMac]

A Fusion drive will not have a 512GB SSD.
If you have 2 or 3 TB fusion drive, the SSD portion is just 128GB.
If you have the smallest 1TB fusion drive, that comes with a 32GB (!) SSD.

Do you still think it would be worth your time to de-fuse the 2 drives?

 

[Berenod]

Plus, the ssd part is used very intensively, especially on the smaller 1TB fusion drive with only 32GB ssd.
They tend to wear out before the harddrive part!

 

[kenfused]

I see! I thought it was bigger but misread the specs. 128GB should be good enough for the OS, but if my mechanical HD is failing on the fusion, what is the best way to rehab the mac?
Options : 1: Go External SSD and boot off it and ignore the failing fusion drive
2. Replace the failing mechanical SATA drive with an SSD (which one?) and de-fuse and ignore the 128SSD ?
- or use the 128SSD for the OS and Apps only and everything else on the SSD
3. Remove the dying SSD and replace the 128GB SSD with a 2TB one.

Any recommendations on brand/model for SSDs? Thinking Samsung.
Thanks

 

[kenfused]

Plus, the ssd part is used very intensively, especially on the smaller 1TB fusion drive with only 32GB ssd.
They tend to wear out before the harddrive part!

Drive Dx says my 128GB SSD of the fusion has 80% life left

 

[ovbacon]

I had a similar issue with my 2015 27" iMac... in my case the ssd was failing and so after some back and forth with people I was able to run my iMac completely from an external 2tb ssd... HERE is the thread of how.

 

[George Dawes]

I had three minis pack up due to their god awful crappy fusion drives

Worst thing Apple ever made imo , thank god everything is ssd only now

 

[DeltaMac]

You will see a lot of threads that suggest moving everything to an external SSD. You will get decent performance from that, and it is a good-enough solution. I have done several iMac upgrades. 2012 and later iMacs are not simple to upgrade, and there are a lot of reasons to avoid an internal upgrade. But, I think if you are careful, an internal upgrade will get a better outcome, including a memory upgrade, should you want to do that. If you get inside, I think the best upgrade (best performance) will be replacing the blade drive. Those with the Apple-proprietary connector are still more expensive, such as those from OWC. Those that I have upgraded were standard NVME. You will be fine with Samsung. I just replaced an iMac internal blade with a Samsung 970 EVO. You have to use an adapter to fit the blade to the connector. Look for a Sintech small NVME-to-Apple adapter. Easy to find on Amazon. I have used those on every upgrade on Macs that need an adapter.
More info here: https://forums.macrumors.com/threads/a-list-of-successful-imac-27-2012-2019-ssd-upgrades.2162435/
As the iMac has to be completely disassembled to get to the blade, then (if you have a 21.5-inch iMac), you should consider upgrading the RAM. It is completely open, and makes sense to upgrade the RAM while you are inside. The 21.5-inch iMac can be upgraded to 64GB RAM. 2 slots, so 32GB x 2. RAM access is not an issue for a 27-inch, but hatdoesn't change the need to disassemble completely to upgrade the SSD blade.

 

[dudax]

... if you have a 21.5-inch iMac ...

On a 21.5-inch iMac, the upgrade is not worth it, that's my opinion.

 

[DeltaMac]

Everyone has an opinion. Mine is different.
I think you have never experienced the "joy" of using one of those 21.5-inch iMacs with the basic 1TB hard drive. Replacing a 5400 rpm hard drive with an SSD is a definite improvement. The iMac user ultimately decides if upgrading the existing iMac is worth it.
I have done a variety of upgrades on 5 or 6 iMacs for friends, and I enjoy the task.
The first one was a big challenge, but after doing one or two, it's pretty simple. Just a few things to be careful about, such as remembering to go slow, so you don't miss any of the steps. You don't want to take one apart (again) because you forgot to connect the camera (Yes, I did that - once!)