Reply to post: Control plane for shared (networked) DAX storage?

Hopping the flash stepping stones to DIMM future

Steve Chalmers

Control plane for shared (networked) DAX storage?

The limit as the stack approaches zero instructions executed per persistent read or write, when the byte addressable persistent memory is shared by many applications running on many servers, is that we will have what network people would call a "control plane" spanning server, memory semantic network, and storage system.

The "control plane" (the drivers) would set up protection and mapping tables to give specific (user space) processes read and/or write access to specific regions of SCM in the storage system. (The "data plane" as a network person would call it is thus read and write operations being performed directly by the application (more likely its libraries) to the SCM itself, with no intermediaries executing lines of code -- not in the server, not in the network interface, not in the switch, and not in the storage system.)

There is an example of how such tables would work in the Gen-Z spec, but I would expect an industrywide control plane to work equally well with PCIe based fabrics, as well as memory windowing and its descendants on InfiniBand and Omni-Path, and other similar technologies reused from supercomputer fabrics.

So who's working on a piece of code that can be the start of this control plane for storage? Hint: if done right, very efficient container storage falls out: storage access permissions aren't controlled by LUN by server as we did in Fibre Channel, they're controlled by memory range (more likely page table) and process, as is sharing of memory between processes within a single server. What we do not need as an industry is 100 venture funded startups each coming up with their own proprietary way to do this...


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