All disks and sticks I have tested with Open-E show as "incompatible". This is a big stopper in evaluating the software. While it is always possible to attach USB disk for the time of testing, it may be much more difficult to use some internal hard drive. As a rule, there is only one, with the main operating system on it. First, it cannot be wiped, second, explain me how to test RAID 6 with one drive.
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.