It's interesting to see many concepts and general design philosophy of exokernels make their way into modern systems. Zero-copy, mmap, RDMA, vectored I/O, fibers/switchto, FUSE - all of these are attempts to push as many policy decisions into user space as possible so that the OS only deals with securely multiplexing the hardware.

The irony is that rather than new kernels, these are being added on as new APIs to the Linux kernel. I suppose that makes a lot of sense because it's much easier to expose a new syscall and see if it gets any adoption rather than convincing everybody to switch to a whole new OS.

It looks similar. MIT's Exokernel seems to use kernel-level hooks to control access to things like disk blocks and network packets. Arrakis takes a similar approach, but restricts those hooks to a subset that can be implemented in hardware instead of in the kernel.