If you don't see this option change the RAID option in BIOS (F2) to RAID ON. Go to the Actions Menu and create RAID Volume from an existing hard drive. It mainly says to download and install the Intel Matrix Storage Manager. support/edocs/systems/ws t3400/en/ug/ug_en.pdf
I know this is late but, in case someone like me is looking for the answer it is on page 56 of the Dell Precision™ Workstation T3400 User’s Guide.
