Legacy Dell OptiPlex systems that utilize chipsets capable of supporting RAID arrays respond to hotkeys (CNTL + I, UEFI F12 Configuration options etc.) when RAID ON is enabled in the BIOS. These hotkeys provide access to the chipset controller interface to configure and manage an array at startup.
Starting with the OptiPlex 3040, 3046, 5040, 3050, 5050, 7050 systems, newer OptiPlex systems no longer present an option for, nor respond to hotkey combinations while operating in UEFI mode, even when RAID ON is configured in the UEFI BIOS.
Note: Dell has never shipped OptiPlex 3040, 3046, 5040, 3050, 5050, 7050 systems (and newer) in a RAID configuration. RAID arrays were not supported as a configurable option at the time of purchase, though several models can be successfully configured with RAID as the chipsets are capable of supporting a basic stripe or mirror array (0 or 1). Not all chassis support the necessary number of storage drives to create an array despite utilizing a supporting chipset. Reference the system manual to confirm physical support if an array is desired.
Note: The RAID ON setting in the BIOS will enable the RAID chipset functionality in both UEFI and Legacy modes, but this setting is intended to support Intel Rapid Storage Technology (IRST) drivers for a M.2 Non-Volatile Memory Express (NVMe) solid state drive (SSD), not a RAID array. Enabling the RAID chipset to support M.2 devices does not imply the system can or will support a RAID array natively. In order to create a RAID array, a dedicated RAID controller add-in card should be installed in systems that provide chassis space to accommodate more than one physical hard drive.
As a workaround to the supported non-RAID configuration on OptiPlex systems, a general set of instructions for accessing and configuring the RAID controller in UEFI environments can be found in the Knowledgebase article: How to access the RAID controller setup in UEFI configured systems .