Hi [NAME],   The part# W9MNK that you gave is listed as one of R720XD components.    I believe it should work, as in detected but negotiated at 6G speed. I suggest to update the server's firmware (iDRAC/LCC, BIOS and H710). 
Hello,   I have the R720xd server with H710 controller.Can i use SAS hdd 10k 12gbps 2,4tb Capacity to this server?I understand that it wont work with 12gbps but i just need it t o work properly.   Thanks a lot, Stefanos   
R720xd with H710 Controller Can i use DELL SAS 12gb 10k 2,4tb 2,5"