With which new PCIe SSD's can I upgrade my Imac 2017 1TB fusion drive?

This scares me a bit:

The rotational aspect of the Fusion drive is a traditional 3.5 inch drive tray in the iMac, but its SSD component is underneath the motherboard in another area of the iMac and you are looking at entire disassembly of the iMac to get to that SSD interface. Lots of opportunities to permanently brick your iMac by tearing it apart.

I do agree about the external PCIe/SSD and I have found that there are Thunderbolt PCIe-drives in which many a 'blade' can go.

It is indeed just the opportunity of the machine already going to be opened. No difference will be felt in speed with a large internal drive and gives more flexibility (future life that is . . .).

• So is it harder then to replace the 24GB PCIe card than the 1TB HDD because the latter is more accesible?

Even when a shop does it, I reckon it is better to stay away from complicated steps; the risk could be too high then. Five or six cables and cable-harnesses to be taken apart and placed back again compound in a very sharp rise in a MTBF calculation.

• My former machine was a 27", adding memory was a simple job. Now this 21.5" is a hard nut to crack.

I have an apple Mac-service point that will replace the memory and the SSD and leave the HDD in place; I now get that is not the most reasonable. For the same amount I can get a 500GB SSD.

Thanks for these answers, also about the two drives really being adjacent to each other, like Jeffrey says. So there is no scary part then.

My options - so far

1. 500Gb PCIe Gen3 x 4 from WD-Blue SN550 Nvme 500 GB, M.2 2280 --> great buy but not sure if it is compatible
2. 2TB Crucial PCIe 2TB Gen3 x 4  is € 240, 1TB . --> best value, probably safe bet
3. 2TB Sabrent Rocket Q 2TB Gen3 x 4 --> great value too , although marketed for the gamers on a PC platform it seems.

The WD Blue looks good, I am not a heavy user, but I read that people have had to format it in several steps. Now that is a deterrent; WD has no info on MAC use, just PC use.

So. Does not look like a great out-of the box solution; on the other hand, OWC is great but three times as costly.

Sorry: X- 2TB OWC, nor Samsung 970 EVO Plus  these - are farrr toooo expensive (2TB = € 600-660, come on);  so expensive I would drop the whole idea. That makes me drop the 500 GB option too.

I agree , investing in a 500 GB Sata-SSD is well spent for sure (e.g. for a second bootdrive where I keep Catalina if Adobe Lightroom won't work with the Big Sur.).

I think I will agree with you, do the 480 GB version, close the box and get an external ICY Thunderbolt house for the photodrive (I now have a 3 TB WD BlueSATA drive for them . . )

reliability is a big issue here.

thanks