The successor is SSDs, and I think for what Apple was using fusion drives for they are worthy successors.

The 2.5” form factor also took up a ton of space in a laptop form factor.

With my NAS box (TrueNAS ZFS) I don’t bother with a cache. I struggle to justify the cost/benefit ratio. The sustained write speed of a 3.5” disk isn’t so bad for the most common NAS use cases.

If I could go back to 2024 I think I’d use a m.2 2280 array for my NAS just because my present tense brain would think it was cheap. I don’t even hoard that much content so 4-8TB would be fine.

Maybe one of these nifty things would be fun: https://www.bee-link.com/products/beelink-me-mini-n150