Thank you for your answer, unfortunately this solution is not for me as the configuration i was planning was for a NAS server, and i already have the 4 hdds. Using SSDs instead would bring not enough storage, even though it would be speedy.
I liked a lot the idea of having a mSATA SSD for the OS, but i found a mini ITX motherboard with the same chipset (Q77), but with standard ATX power connector, and 6 SATA connectors, so i can use a more traditionnal 2.5" SSD with this solution, and also my 4 HDDs.
I dont't need thin ITX form factor, so the DQ77KB is not the one for me...