Slower write to server after setting up link aggregation

Hi all,

So first off, I'm fairly new to this kind of network stuff, so I might have just overlooked something basic, but I've setup link aggregation for my Unraid box and I can pull data from the server faster as a result, but my writes to the server have been slowed down to less than half the speed I had with a single gigabit connection. Here's the details:

- Server has quad-gigabit NICs onboard, these are set to balance-rr in network settings. 

- PC has an Intel I350 based quad-gigabit NIC installed, with link aggregation setup through the Intel PROSet Adapter Configuration Utility. I can verify through Windows Network and Sharing Centre that the link speed is 4Gbps.

- My switch is an HP ProCurve 1810G-24 J9450A, with two trunks setup, one for the server and one for the PC

Transferring large files such as videos from the server to the PC maxes out at about 2.8Gbps, with a more typical speed bouncing between 2-2.3Gbps. Writing to the server I get in the neighbourhood of 400-500Mbps. This is with SSDs only in the PC and writing to and reading from a test share that is set to cache only for the purpose of troubleshooting, so drive speed shouldn't be causing me any issues here. 

My theory is the issue lies somewhere on the Unraid side, as unplugging all but one network cable between the switch and server sets it back to a single gigabit link, at which point I can read from and write to the server at gigabit speeds again. Are there any specific changes I need to make in the Unraid settings to better optimise for multiple connected network ports? 

I'd really like to get this issue resolved if at all possible. I'm far less concerned about my read speed from the server than my write speed to the server, since I write to it far more often than I pull data off it, but if I can get both working at or near 4Gbps that would be awesome. 

Any suggestions much appreciated, this is my first forum post so if I've missed anything important I should have included please let me know and I'll add details ASAP.