Hard to find a solid answer about this. Reading this & this you kinda get the idea RTX IO, MS Direct Storage and a 3500 mb/r SSD would do it… but there’s no real confirmation though …
On the demo’s they specifically state it’s running on a PS5 / Series X, and their party piece is that super fast SSD ( comparable to a PCI gen 4 SSD on the PC )
Am about to pony for a laptop, that doesn’t have PCI gen 4 though … if it can’t do Nanite, I’ll need to look for a different model…
I believe this is like asking how much does a sack of flour weigh, its likely based on how dense a mesh is and the screen resolution.
Any NVMe Gen 3 SSD will be more than fine.
And even HDDs can run Nanite if you have enough RAM.
I ran the UE5 demo on an HDD, it was fine. Although I had 32 RAM.