2017 iMac and fusion drive options and queries

[Chagzuki]

I bought a second-hand 27inch 5k 2017 iMac which has a 1tb fusion drive, running Mojave. I’ve generally been a pc person in the past so there’s a learning curve involved for me with all things Apple.
The seek times for the hdd portion of the fusion drive is a clear bottleneck which I’d like to rectify via an ssd upgrade. So I have the options of either installing a Sata ssd or a PCIe ssd. If I install a Sata ssd I’d have that plus the current 24GB PCIe ssd. I don’t have any means to benchmark the fusion ssd and I’m under the impression that specs have varied over the years, so I don’t know if it’s significantly faster than a Sata ssd. I’m wondering if it would make sense to use the current PCIe ssd for system files and a Sata one for media files... though 24GB is probably too small for system files, unless it’s possible under macOS to install apps to other locations. Another option would be to create a fusion drive from the two ssds... might this make any sense whatsoever, or is the fusion drive system really only appropriate for a ssd/hdd combination?

 

[chscag]

Welcome to our forums.

Generally we do not recommend a Fusion drive when ordering an iMac, either the 21.5" or 27" model. Most folks opt for the Fusion drive since it's standard on the later model iMacs and is much less expensive than a pure PCIe
SSD.

If you're a handy person, you can remove that Fusion drive combo and replace it with a PCIe SSD of the same size (1 TB). Not an easy task by any means but you might want to look over the procedure and see if you're up to it.

Go to iFixit: The Free Repair Manual and look up the procedure for your model.

As to creating a Fusion drive with 2 SSDs, I don't believe that's possible.

 

[harryb2448]

As chscag says it is not possible to fuse 2 x SSDs, must be one and a platter drive.

With only a 32GB Blade Drive, better to ask first as this will noit hold a full operatring system and the iMac decides what goies on the blkade and what on the slow old platter.

 

[Chagzuki]

Thanks for your responses.
Another possibility I see mentioned is to leave the hdd inside as a Time Machine backup drive. I'm curious, if this were the case, as to what percentage of the time the drive would be active and how much in sleep mode, since I dislike the noise of mechanical drives... plus the energy consumption isn't optimal.