Very recently I setup a mergerfs mount for this. It’s very crude for my use case but works perfectly and I could use the existing volume as is.

I got partway thru setting up a script to copy recently accessed files from the HDD to the read-prioritized SSD.

My LLMs load up way faster, and I still have a source of truth volume in the huge HDD. It’s not something I’d use professionally though, way too janky.