Low transfer speeds on DSM 5.0

[evolucja]

Does anyone has any idea why I'm getting such strange trasnfer speed results with following configuration?

 

- DSM 5.0u5

- Nanoboot (5.0.3.2)

- Q1900-ITX + 2GB RAM

- 2x3TB WD GREEN in RAID1

 

I made a ISCSI drive and performed a test. We can see the network is capable of full 1Gbit speed, however the transfer varies a lot during operation so the avargade result is dissapointing..