On large files (multi GB), I got 34MB/s average from the NAS to VM. And 54MB/s from a share on the Win10 host to ArcaOS guest. Those are only about 272 and 432 Mbps respectively. I should be able to at least get Gigabit speed on the LAN and local share, and hopefully more, but it seems the networking in Virtualbox is just too slow. I might get faster results with iperf and/or netio as it would take the SMB out of the picture.
So, I broke the Gigabit limit on my LAN in my OS/2 VM.
Here is how I did it :
1) upgraded to Virtualbox 6.0
2) noticed there were new additions with a VBOXFS.IFS for shared folders
3) shared my X: drive from my Win10 host to ArcaOS guest as X: also .
X: is a share mounted from my Ubuntu NAS to the Win10 host.
4) ran my file benchmark again, on a 4.5GB ISO movie file
I averaged 243,677 KB/s , which is 1949 Mbps , or about 2 Gbps. This is consistent with what I was seeing in the Win10 host task manager - network bandwidth at 2 Gbps .
Subsequent runs are even faster, because the Win10 host is caching the remote file : 608,601 KB/s . This is about 5 Gbps . In this case there as 0 network bandwidth usage, though, due to caching.
That means I have to try with files that don't fit in the host's RAM (32GB), or just try with different (uncached) files each time.
I didn't try yet sharing a local drive to the VM yet. I have a striped array of SSDs which does 2600MBps sequential (about 21Gbps) in Crystaldiskmark 6 for sequential test. My guess is that I will hit a bottleneck much lower than that in the VM.
Just tried it, since adding shared folders don't require a VM restart.
I was able to read a 35GB file, uncached, at 656,854 KB/s from the local SSD array. I tried again with a 2GB file, twice to make sure it was cached, and got similar speed. So, 5 Gbps appears to be the upper limit for the shared folders in Virtualbox.