Weird file transfer issue

[outsider]

I decided to install FreeNAS corral as a VM on unraid so I can play with it. I gave the FreeNas a dedicated SATA controller card and attached a bunch of HDs to it.

Setup a simple ZFS volume and a test share.

While doing some file transfer tests, I'm finding a weird discrepancy which I can';t explain.

 

Network topology:
Workstation PC (running Win 10) --> 1GB Ethernet --> Unraid 6.3.3

Windows 10VM (running on Unraid)

FreeNAS Corral VM (running on Unraid)

(The Windows 10 OSs, Unraid and FreeNAS are installed with the basic installation defaults. No customization was done for network behaviors.)

 

Benchmarking:

The test file was just shy of a 1GB.

I copy the test file from Workstation PC over ethernet and I get 113MB/s write to Unraid (it's writing to a SSD cache disk) 

I copy the same file back from UnRaid (from cache SSD disk) to the Workstation PC and I get 113MB/s read.

This makes sense. I saturate the gigabit connection.

 

I copy the same test file from the Win10 VM to  and I get 130MB/s write and 180MB/s read to the FreeNAS zfs share on the FreeNAS VM

This also makes sense. Since both VMs are on the same hardware, I'm likely getting to the read/write limit of the HDs.

 

Now if I copy the test file from the Workstation PC over the LAN to the FreeNAS share, I only get 80MB/s write speed. (Read speeds over the LAN are 113MB/s, as expected)

 

What would cause this limiting in transfer speed when I know the array can be written to faster and I know the ethernet connection can also handle faster transfers?

What would you do to get to the bottom of this weird limitation?

 

Edited April 16, 2017 by outsider