Thanks for the detailed reply. I found a QSFP+ DAC that says it supports IB and Ethernet.
I don’t have enough computers to set up a fabric, only the 2 I would be direct attaching have PCIE slots.
I’ve never used infiniband before so my reason for wanting to try it is just to learn what it is, and how it works. That said, some of those use-cases look very interesting, especially transporting NVMe namespaces, I didn’t know that was possible.