Why Specifically QDR IB? Are we discussing the virtual link between VMs? (I haven't used ESX since 3.5 so maybe they now have a QDR IB driver?). I ask because I have SDR and DDR IB equipment I'm setting up to use on the server so clients have decent speed to the array (my tests with SDR hit 700MB/s+). I have a IB switch (SDR) I'll probably use but if I went Point to Point it could be done with a DDR speed link.Yes, but your slowest link is still iSCSI so the SMB3 multi-path may not be of help. I can see doing OI with vmxnet3 to windows 2012 with vmxnet3 to leverage multiple 1GbE links. If you only have one or two clients, going with QDR IB from OI server to client seems like a less complex and higher throughput solution though.
The main reason I was thinking about a weird roundabout SMB3 attempt was so 1 particular PC that is outside the range of a CX4 IB cable (its just to long a run) could still get fast speeds with a bundle of cat5 Honestly I'll either move it so IB can reach or later on I'll pick up some 10GbE fiber stuff and make a fiber run since its max length is far far more then I'd ever need.