MPIO - slow speed

Hello!

I have two ReadyNAS6 Pro boxes with the following configs:

1 box

RDN6 pro/E7300/4gb/6*2Tb WD CB/4.2.27 FW

2 box

RDN6 pro/E5300/2gb/6*2Tb WD CB/6.3.5 FW

Other equipment:

Juniper EX3300 switch and Dell R510 server

R510 is Hyper-V 2012 R2 server for lightweight load  with MPIO enabled.

I'm using SQLio to check iSCSI storage speed and latency.

while any tests I got only ~110MB/sec storage speed with 2*500mbps load at dedicated iSCSI NIC (taskmgr) with any NAS.

mpclaim show LB policy as RRWS (it seems to be correct, but RR only is unsupported??!) with two active paths, so MPIO configured correctly.

But PRTG monitor shows ~92-95% load at first NIC and ~10-15% at second NAS NIC, so why I guess there is some MPIO error with NAS config.

So, the question is: how to achive 2*1gbps speed using MPIO with ReadyNAS?