How will a fusion drive work if you have two partitions with two Mac OS's???

[RLRL]

I have an late 2013 iMac, still runs perfectly, with a 1.12 TB fusion drive (121 GB SDD, and a 1 TB HDD).

If I partition this drive, partition 1 El Capitan, partition 2 High Sierra, how will this Fusion drive work.

Does the SSD get partitioned? Do both OS's use the SSD? I have no idea how a fusion drive works with multiple partitions.

Can you even partition a fusion drive?

Comments

 

[joevt]

I think with Fusion drives, only one macOS is fusion. Everything else exists on the HDD.
There may be ways to create multiple fusion drive containers using the diskutil command. This would probably require having two partitions on the SSD and two partitions on the HD. Then you create the Fusion container using one partition from each.
I have never tried this. I have not done much research.
Type diskutil in Terminal.app, select the word diskutil, right click the selected word and select "Open man Page" to see more info about the command.

I would replace the HD and SSD with larger SSDs and not use Fusion drives. I did this for my iMac (27-inch, Late 2013) so now it has 1TB SSD (NVMe) and 2TBSSD (SATA).
www.macsales.com has upgrade kits and video instructions. Click "My Upgrades", enter your Mac type and model, then click Internal Drive options. One of the kits you buy should include adhesive strips, suction cups and all the other tools needed to open the iMac. I bought two such kits (one with NVMe SSD and one with SATA SSD).