Unifi 10Gb Link Issues

Hi All,

Firstly I apologize in advance for my inadequacy... I am somewhat new to networking at a business level.

I am setting up a portion of our network using 10Gb fiber links. We currently have a Unifi USW-Pro-48-PoE connected to a Synology RS1221+ via a 10Gb fiber link, using Unifi UF-MM-10G SFP+ and a Mellanox MCX311A-XCAT CX311A ConnectX-3 NIC in the NAS. Additionally, I am trying to connect a PC to the second SFP+ port, also using the same SFP+ modules mentioned above.

My questions are:

• When connecting the fiber, it seems as if there is an order of operations. I need to connect the fiber to the end device (NAS or PC) first before connecting to the switch. If not done in this order, the link will not establish. I have done other 10gb fiber type stuff (Underwater research) and I do not remember this being an issue.
• When an SFP+ is installed in SFP+ slot #1, if I install a second SFP+ in slot #2, the link in slot #1 drops. Is this expected behavior? If I unplug and replug in the fiber on the NAS, the link reestablishes.
• On the PC, when performing an Iperf3 test, my maximum bandwidth is about 3.25Gbps. I would expect the link to saturate at upwards of 7-9Gbps. This is using Iperf with TCP setup.

Any thoughts? Again, I apologize for my shallow depth of knowledge here...

Thanks!