A rescan on the server's RAID controller is a possible troubleshooting step to detect the existing RAID configurations on the connected storage arrays. A firmware upgrade may cause the RAID controller to lose the RAID metadata or settings, and a rescan may restore them. A rescan is preferable to restoring the default RAID configuration, as the latter may erase the existing data on the arrays. Power cycling the storage arrays or booting the OS into recovery mode may not help if the RAID controller does not recognize the RAID sets.