It is possible that the disk has failed but the best way for us to be 100% sure is if you can run a DSET report on the server. That way we can look at some log files and be able to see what caused the drive to fail if indeed it is in a failed status. If you are not familiar with DSET you can get it at www.support.dell.com/dset Once you get that ran I can provide you my direct email and you can send it to me to review for you. Please let me know if you have any further questions or concerns. 
Hi, We have MD1220 Enclosure connected to Dell server. I used SUU_721_Q12013_A00 to update disk firmware from DE06 to DE08. One of the disk failed to update firmware and after server reboot I do not see it in OpenManage server administrator. It showed DE06 version before reboot (but disk was failed with red X) even no errors were provided in SUU after firmware update, all successful. As I cannot access server and enclosure physically could it be that disk failed and need to be replaced, or it is another reason why after unsuccessful firmware upgrade it does not appear on OpenManage? Thanks
Is it disk failure?