Keep in mind that local storage is getting lower latency year over year. NVMe was a big step, but there could soon be more hardware memory mapped flash storage

Keep in mind that local storage is getting lower latency year over year. NVMe was a big step, but there could soon be more hardware memory mapped flash storage (like DIMM SSDs), and 3D XPoint. I think the overhead will soon exceed the operation in terms of cost, especially if it's asynchronous.