I had an external RAID5 array attached via USB 3 to a Windows 10 PC and I could get 220 MB/s read and write performance.
I attached this same RAID5 array to a computer (ROCK64 = 4 x Core ARM chip with 4GB RAM) running OMV4 via USB 3. This OMV4 computer is connected to my other computers via Gigabit Ethernet.
Using SMB/CIFS I get 90 MB/s read and write out of my RAID5 array (40% of the performance).
Using NFS I get 12 MB/s read and write out of my RAID5 array (only 5% of the performance). Unfortunately I have a linux application that is very specific and will only work over NFS...
I expected to loose a little performance going over a network and through another computer, but nothing like this.
Since I have a UPS in Windows 10 I chose the following device options to improve the USB performance: "Enable write caching on the device" and "Turn off Windows write-cache buffer flushing on the device"
In OMV4 is there a way to check the underlying performance of the RAID5 array to take the network out of the equation and have a fair comparison?
In OMV4 is there a way to improve the performance of external USB hard disks devices?
In OMV4 is there a way to improve the performance of NFS to something acceptable?