NVMe-oF Multipath support

[hydro-b]

SPDK has support for NVMe-oF Multipath since release v22.01. It would be great to have support for this added to ceph-nvmeof. With multipath support a highly available solution could be made without the need for LACP on the client / server and MCLAG support in switches.

[PepperJo]

We are in the process of adding multipath support. The SPDK support you are mentioning is for a single SPDK instance (cf. https://spdk.io/doc/nvme_multipath.html). While it is useful in some scenarios, we are focusing on gateway grouping, i.e. the possibility to start multiple Ceph/NVMeoF gateways that share the same configuration (meaning they export the same subsystems/ns etc.). With this setup we will have NVMeoF multipathing to multiple SPDK instances and you will be able to set ANA for each path. We are also working on a discovery service to allow an initiator to gather the path and get notified on path changes.

[hydro-b]

@PepperJo That's even better! That would make for a true HA solution.

[sdpeters]

This would provide at least part of the requirement in https://github.com/ceph/ceph-nvmeof/issues/113