If you change to UEFI, you'll need to reinstall the operating system. UEFI changes completely how the OS reads the system hardware, so there's no avoiding a reinstallation. Updating the firmware will not impact the RAID array.
Good afternoon. Currently we have 8 x 1Tera disks in our PorwerEdge R510. - 1 RAID 1 for the 2 first disks, wich have the OS(Windows Server 2008) -1 RAID 5 for the other 6 disks We are trying to upgrade our RAID 5 with new 6 x 3TB disks. The problem is that OpenManage reports that the disks that we inserted are 2TB, and the state is "unsupported". Screenshot:  The firmware of the PERC H700 is: Firmware Version 12.0.1-0091 Driver Version 4.31.01.64 Storport Driver Version 6.0.6002.18005 Do you know why is this happening? Do we need to do a Firmware update to the PERC Controller? If so, will this erase RAID 1, the OS disks? Thanks in advance for your help! Cheers. 
3TB disks for DELL PoweEdge R510 with PERC H700 Controller