Low cifs performance

[Mats]

Hi,

Freenas Spec
Gigabyte GA-F2A88XM-D3H R3.0
AMD A8-5500
32Gb memory
LSI MegaRAID 9211-8i 2.0 SAS/SATA
5 2Tb Samsung HD204UI
3 2Tb Seagate ST2000DL003
2 2Tb WD20EZRX
Intel NIC EXPI9301CT

When copying small files like mp3 5-10 Mb i only get a file transfer of 40-50Mb/s
I copy from windows 7 to the freenas

Why is it so slow?
I have checked the autotune but that did not increase the perfomance.