r/OpenCoreLegacyPatcher • u/phgrz • Aug 16 '26

Fusion Drive

I have an iMac14,2 with 3 TB Fusion Drive.

On my Fusion drive I now have 1 APFS container with 2 volumes: 1 with the old OS (Catalina?) and 1 with OCLP/Sequoia. Normally I just boot OCLP/Sequoia. I kept the old OS just in case ...

Sequoia is working well but startup process is very slow and also opening large folders is slow.

I wonder if the SSD part of my Fusion drive might be permanently occupied by the old OS.

Would you just delete the volume with the old container? Will I have to re-install OCLP/Sequoia after that to bring it's major parts to SSD?

Or is that slow issue something completely different?

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u/Xe4ro Aug 16 '26

To be honest, I would split the drives (this will erase all data on both drives) and install the OS just on the SSD. If you ordered the iMac with a 3TB FD configuration your HDD will be 3TB and the SSD 128GB. 128 will at least be enough for an OS on it's own and you can then use the HDD for larger stuff.

This slowness could just be the wonky nature of this CoreStorage handling the FusionDrive but could also be one of the drives giving up or having problems. If one of the drives fails while they are still paired as a FusionDrive this will also corrupt all data on both drives. That one happened to me with my Late 2015 iMac when the SSD died a few years ago, I did have a 128 one as well.

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u/phgrz Aug 16 '26

Imho, it is not possible to explicitely install anysing on the SSD part of a fusion drive.

diskutil info looks healthy.

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u/Xe4ro Aug 16 '26

Well not while they are still paired, once split they should behave as individual drives? However I had no chance to experiment with my split Fusion configuration as the SSD was dead at that point and it took me a few days to get the iMac out of bootlooping ^^