Disk Cache vs Render Cache Fusion Output?

Whats the difference between "disk cache" option in the Fusion page and the "Render Cache Fusion Output" Auto/off/on option from the edit page? The "render cache fusion output" is not even mentioned or explained in the manual that I can find.

Nobody knows??

I would like to know the answer to this as well. It seems to me that there is no communication between the cache on the Fusion screen and the cache on the Edit screen. I can successfully cache various nodes in the Fusion screen and have it play back in real time, but none of that is carried over. Make editing with Fusion clips really a pain. Also, it doesn't seem like you can cache Compound clips on the edit screen, which also seems weird. This whole cache issue is probalby the major reason our team hasn't switched form Premiere/After Effects yet.