Slow SMB performance
Unraid SMB performance is very slow compared to SMB performance of a Windows Server VM running on the same Unraid hardware.
I tested using 6.7.0.
Test methodology and results are here:
https://blog.insanegenius.com/2019/06/10/unraid-in-production-a-bit-rough-around-the-edges-and-terrible-smb-performance/
server-1-diagnostics-20190611-0254.zip
Minor
There are different solutions to enhance performance (impact descending):
enable SMB Multichannel + RSS (this enables multi-threading, which allows transferring multiple files simultaneously instead of only one by one, which is the default in Windows, but not with Linux)
use Disk Shares instead of User Shares (which avoids Unraid's "FUSE (sshfs) overhead", which can be massive)
enable case-sensitivity (this allows co-existence of "photo.jpg" and "Photo.jpg" in the same dir