Hey,
In case using mixed networks with iSCSI, we usually recommend going with Failover Only multipathing policy. In this case, 1 GB interface will only be used in case of 10Gb link failure.
As for specific mulitpathing settings, you should check it with Storage vendor. Different vendors can have different recommendations. I haven't found anything recent from Qnap, so it might be better to contact their support.
You can add storage redundancy to your configuration by using StarWind VSAN as a shared storage. VSAN will create replicated shared storage pool and share it via iSCSI with Hyper-V hosts. In this scenario, your setup will be able to tolerate storage failure. Might be helpful: https://www.starwindsoftware.com/best-practices/starwind-virtual-san-best-practices/
Cheers,
Alex Bykovskyi
StarWind Software
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