ZFS will happily use a large amount of RAM for caching if you have it, but it'll run fine on a recent Pi (3 or 4, or not raspberry at all).
It'll run fine but more sadly on older Pis running 32-bit kernels, since it does a looooooooot of 64-bit and wider operations, so you pay a nasty tax on that on 32-bit things. (Though the virtual address space limits might actually be sadder than the 64-bit operation penalty there, really...)
It'll run fine but more sadly on older Pis running 32-bit kernels, since it does a looooooooot of 64-bit and wider operations, so you pay a nasty tax on that on 32-bit things. (Though the virtual address space limits might actually be sadder than the 64-bit operation penalty there, really...)