Why is the upload speed low through iscsi?

Question

HP

in general, the situation is this, there is a "storage" in it is intel x520da, inside the system the speed of the disks shows 800/700 megabytes, I made an iscsi target, I connect from another machine to the target, I test the speed, read 700, write 300. The network boots to 7 and, accordingly for 3 gigabits, the question is why is the return so sagging?
Now iscsi is raised on hp 360 g5 (e5405x2 / 16g Ram) percent is loaded during tests by 20%. 10 disks are connected to the lsi 9620 controller. Before that, I wanted to do it on hp360 g7 (x5620 / 32g Ram) but it freezes when loading along with the controller, and continues to load if you press F11 (Boot menu). As soon as you take out the controller or put in adaptec, then everything is loaded normally, what could be the problem here? when I tested it on the G7, the iscsi speed was close to the local speed, i.e. 1000/800