3 ms·

How is far memory different from a disk?

• xiii1408 7y ago
  Disk could be considered a specific form of "far memory." In the context of this paper, though, "far memory" is referring to memory outside the local system that is accessed using RDMA instructions.
  • deffbjinnnbbvf 7y ago
    Don't disk-based data structures have similar constraints? There too there is no ability to ship computations and we try to optimize for minimal data round trips.
    • xiii1408 7y ago
      RDMA instructions are (1) more expressive than disk operations, from what I understand (support compare-and-swap, fetch-and-add, etc.) and (2) have different latencies and bandwidths (on the order of 1us latency, 20 GB/s BW). This paper is mostly about proposing new RDMA instructions, such as a relative load/store, that could make remote data structures more efficient.
      • wtallis 7y ago
        NVMe defines compare and atomic compare-and-write operations, but I'm not sure if there are any notable users of them. They certainly aren't exposed by typical file IO abstractions. There's nothing like a fetch-and-add in any typical storage protocol that I know of.
• deleted 7y ago
  [deleted]