I just upgraded an existing OMV6 NAS setup into a new case with a different motherboard and more RAM. Everything seemed to be working well but after more testing I found a big problem with uploading via FTP.
Background: I have a desktop PC running Mint 21.3, a server running Xubuntu 22.04 and the OMV6 NAS. After reading another thread which mentioned iperf3, I installed it on all three machines. The test results are below:
Speed between Mint PC and OMV NAS - 930mbits/s
Speed between Mint PC and Xubuntu - 936mbits/s
Speed between Xubuntu and OMV NAS - 937mbits/s
This suggests to me that the Gigabit NICs in each PC and Gigabit switch are working properly.
Using Filezilla, I tried to upload a 3.2GB file from Mint to OMV6. It started copying at 110MB/s but dropped to 18MB/s after 5 secs or so. I tried copying the same file by the same method to the Xubuntu server (also using ProFTPD) and this ran fairly consistently at 116MB/s. Once that completed, I tried sending the file from the Xubuntu server to OMV6, again using Filezilla.. It started copying at 105MB/s and dropped to just 18MB/s after a few seconds. This does suggest that the issue lies on the machine running OMV6.
The motherboard is an Asus P5G41T-M LX2 and the manual says the NIC is a Realtek RTL8112L Gigabit ethernet controller. Am I looking at a bad NIC driver or something like that?
Can anybody suggest a solution?
Update:
I tried a PCI LAN card (TP-Link TG-3269) and this was just the same. After removing it and re-enabling the onboard NIC running omv-firstaid reported no network interfaces found. I fitted the TG-3269 back into a PCI slot and on booting BOTH NICs reappeared. Uploading a large file to the NAS slowed down to 18MB/s whichever card I connected to.
I added a USB to Gigabit network adaptor to the mix. It was plugged into a USB 2.0 port (there are no USB3). Using iperf3 as above, the speed between PCs on the same LAN was around 310mbits/s - a third of the speed of the other NICs. Despite this 'handicap' uploading to the NAS managed a steady-ish 20MB/s after starting at around 40MB/s. Despite doing tons of research, this one has me stumped. 
I've tried different patch cables in case I was using a Cat5 one instead of Cat5e and that made no difference. I tested copying to a very old Buffalo Linkstation NAS which only has a 100Mb/s LAN and that stabilised at 6MB/s using Filezilla. I was using the same cable/switch port as the OMV NAS.
Given that I've had trouble with dropping speeds when using Clonezilla too, I am starting to suspect this is related to NIC drivers used by Debian because both OMV and Clonezilla are Debian-based. If this is right, there are very serious implications for people trying to use those two systems.
Since my NAS is an old PC, I can try buying an Intel-based LAN card since Intel is known to be well-supported in Debian. People using SBCs cannot do this because they are stuck with the built-in NIC. Other than going back to my old hardware, I don't know how to proceed.
My latest test was to install OMV6 on a Raspberry Pi 4 - 4GB model and connect a 2TB USB 3.0 disk to it. I connected it to my switch using the same cable as my PC-based installation of OMV6. I copied a 6.2GB movie to it using Filezilla and it FLEW along at a consistent 85-100MB/s. Running iperf3 again gave a speed of 930Mb/s which is about right. The file copied in under a minute. That's what I expect to see rather than the measly 20MB/s I'm getting using a more powerful machine than a Pi4.
