Re: [PATCH v6 00/16] nvmet: add target passthru commands support

Stephen Bates
2019-07-27T00:50:52Z

> This is different from multipath on say a multi-controller PCI device
> and trying to expose both those controllers through passthru. this is
> where the problems we are discussing come up.

I *think* there is some confusion. I *think* Sagi is talking about network multi-path (i.e. the ability for the host to connect to a controller on the target via two different network paths that fail-over as needed). I *think* Logan is talking about multi-port PCIe NVMe devices that allow namespaces to be accessed via more than one controller over PCIe (dual-port NVMe SSDs being the most obvious example of this today).

> But it's the multipath through different ports that
> seems important for fabrics. ie. If I have a host with a path through
> RDMA and a path through TCP they should both work and allow fail over.

Yes, or even two paths that are both RDMA or both TCP but which take a different path through the network from host to target.

> Our real-world use case is to support our PCI device which has a bunch
> of vendor unique commands and isn't likely to support multiple
> controllers in the foreseeable future.

I think solving passthru for single-port PCIe controllers would be a good start.

Stephen