Audriusa, it seems that you are installing the system in a wrong way, so please go to the following link:
http://www.open-e.com/service-and-su...ts-and-videos/
And look for "Installing Open-E DSS V6" to learn more how to install DSS, using USB or HDD ( internal or external ).

If you still have any "incompatible" message, please support us with your hardware details, as it seems you have some hardware issue, and you may need to replace a RAID controller or something.