newsboy

Your desktop downloading from the internet proves that you can at least get 20MB/s over that particular segment of the powerline adapter network. But that doesn't prove the powerline adapter being use with the server is capable of getting 20MB/s. Is there any way you could move the server next to the router, so you can plug it in with ethernet? Or unplug the server and plug a laptop into the same powerline adpater and do a speed test. The laptop test would confirm its not the powerline adapter

Have you tried running ethernet between the two to see if the issue is the powerline adapter? When you say slow transfer speeds what are you doing to determine this? Are you looking at windows explorers estimate? Is this on reads or writes from the rotating disk? Reads or writes from the ssd cache? Are you copying many small files in the KB range or a few large files?

I have found NFS to be unstable. I am running unraid within ESXi. I was originally mounting from fstab, but ended up with a lot of "stale NFS" errors. Form another post on this forum I started using autofs. It seems to have marginally improved, but I still end up with errors telling me a directory doesn't exist, which I believe to autofs for "stale NFS" errors. Just some background, I'm running ESXi 5.5, with NFS user shares, X9SCM, and an IBM M1015 card.