Hi!
I installed OMV for the first time, and I'm experiencing networking problems.
The hardware is a 2012 Mac mini, i7 2.6, 16GB ram, 2 internal SSDs and a bunch of external drives (1 sw raid, 1 hw raid, 3 single drives).
Randomly, the server loses network connection, and the "blackout" lasts for some minutes, then it comes back online. I noticed that it is a systematic thing because if I stream through Plex (docker container on OMV) I cannot watch a tv show episode without having to wait 5 minutes, refresh the page and then play again. Ok, media streaming is not that important, but I'm planning to use it for Time Machine Backup on a Mac, Carbon Copy Cleaner on a Windows PC, and rsync with some directories and repositories from office computer. Having to move GB across the internet can be a pain in this situation.
I can exclude cable/router or hardware problem, because everything was working perfectly under macOS, just before wiping the machine and installing OMV.
In a message during startup I read something about wifi and driver stuffs, thus I opened the computer and disconnected the wifi/bluetooth interface, trying to limit the possible connections only through the ethernet cable, but it didn't solve the problem. then I realized that I could check the syslog 
Here is what is happening during the network blackouts:
May 17 17:41:15 mini kernel: [ 562.776824] tg3 0000:01:00.0 enp1s0f0: 0x00007030: 0x00010000, 0x000000c8, 0x000c0030, 0x00000000
May 17 17:41:15 mini kernel: [ 562.776835] tg3 0000:01:00.0 enp1s0f0: 0x00007500: 0x00000000, 0x00000000, 0x00000080, 0x00000000
May 17 17:41:15 mini kernel: [ 562.776848] tg3 0000:01:00.0 enp1s0f0: 0: Host status block [00000001:00000093:(0000:002e:0000):(0000:0032)]
May 17 17:41:15 mini kernel: [ 562.776862] tg3 0000:01:00.0 enp1s0f0: 0: NAPI info [00000093:00000093:(0136:0032:01ff):0000:(00f5:0000:0000:0000)]
May 17 17:41:15 mini kernel: [ 562.776876] tg3 0000:01:00.0 enp1s0f0: 1: Host status block [00000001:0000003d:(0000:0000:0000):(03ff:0000)]
May 17 17:41:15 mini kernel: [ 562.776888] tg3 0000:01:00.0 enp1s0f0: 1: NAPI info [0000003d:0000003d:(0000:0000:01ff):03ff:(01ff:01ff:0000:0000)]
May 17 17:41:15 mini kernel: [ 562.776901] tg3 0000:01:00.0 enp1s0f0: 2: Host status block [00000001:000000f8:(002e:0000:0000):(0000:0000)]
May 17 17:41:15 mini kernel: [ 562.776913] tg3 0000:01:00.0 enp1s0f0: 2: NAPI info [000000f8:000000f8:(0000:0000:01ff):002e:(002e:002e:0000:0000)]
May 17 17:41:15 mini kernel: [ 562.805262] tg3 0000:01:00.0 enp1s0f0: Link is down
May 17 17:41:15 mini systemd-networkd[470]: enp1s0f0: Lost carrier
May 17 17:41:15 mini systemd-networkd[470]: enp1s0f0: DHCP lease lost
May 17 17:41:15 mini avahi-daemon[786]: Withdrawing address record for 192.168.178.20 on enp1s0f0.
May 17 17:41:15 mini avahi-daemon[786]: Leaving mDNS multicast group on interface enp1s0f0.IPv4 with address 192.168.178.20.
May 17 17:41:15 mini avahi-daemon[786]: Interface enp1s0f0.IPv4 no longer relevant for mDNS.
May 17 17:41:18 mini kernel: [ 565.753744] tg3 0000:01:00.0 enp1s0f0: Link is up at 1000 Mbps, full duplex
May 17 17:41:18 mini kernel: [ 565.753765] tg3 0000:01:00.0 enp1s0f0: Flow control is on for TX and on for RX
May 17 17:41:18 mini kernel: [ 565.753771] tg3 0000:01:00.0 enp1s0f0: EEE is enabled
May 17 17:41:18 mini systemd-networkd[470]: enp1s0f0: Gained carrier
May 17 17:41:19 mini systemd-networkd[470]: enp1s0f0: DHCPv4 address 192.168.178.20/24 via 192.168.178.1
May 17 17:41:19 mini avahi-daemon[786]: Joining mDNS multicast group on interface enp1s0f0.IPv4 with address 192.168.178.20.
May 17 17:41:19 mini avahi-daemon[786]: New relevant interface enp1s0f0.IPv4 for mDNS.
May 17 17:41:19 mini avahi-daemon[786]: Registering new address record for 192.168.178.20 on enp1s0f0.IPv4.
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Any Idea? 
Beside this, I'm running OMV since a week and I find it extremely simple and powerful! I managed to restore all my workflows without a single headache! 