Two Intel X-520 DA network cards, low speed - why?

Question

NAS

Good afternoon.
There are two servers
1. Hyper-v server core 2012r2
2. Nas-free (release 9.1**) - file storage.
Both servers have Intel x520 DA network cards installed.
With the help of the "SFP + Direct Attached Cable (DAC)" cable from NAG.ru, they are directly connected to each other.
In the settings, I specified 10 GBe full duplex on both machines. (Hyper-v: INTEL driver + duplex registry setting)
Nas-free also defines: IX1 "media: Ethernet autoselect (10Gbase-Twinax )"
At one point it happened that after I set the registry settings (set full -duplex 10 gbit in Hyper-V server) and rebooted, everything worked for me.
It worked, the speed reached 8-9 GBe read\write. After combining the port with a virtual switch into a bridge, the speed dropped again.
He suggested that the reason was in the last action, and returned it back.
The speed during the test again did not exceed 500 Mbs.
Tried everything possible.
Checked network cards on other platforms in different bundles. The same situation.
I put the cards on a Windows server 2012r2 with an interface, put it up with my hands and carried out tests, put the second card in Windows 8.1.
The same.
I resorted to solutions Link
Perhaps the point is in the firmware of the network cards themselves. I did not quite understand how to update the firmware for Intel network cards.

Answer 1

How much and what disks does Nas-free and Hyper-v server core 2012r2 cost, what type of raid?