I have a Dell PowerEdge R410 with two SAS drives connected to the SAS controller and I would like that both of them can be in the boot sequence tried to boot. I would like to use md software RAID-1 in Linux so if one disk fails, server should try to boot from the other one. But in the BIOS I see only one hard drive (the first one) in the boot sequence and also in the boot manager I have only one hard drive listed. But otherwise the second hard drive is recognized normally (it is visible in SAS controller) and also in the Linux afterwards. Only booting works only from the first hard drive.
You may need to go into the "host bus adapter" bios and look at the options. When that screen comes up there is a keystroke to go look at the settings. I believe it is control H or perhaps F5-f8.
Once you are in those menus it is simply a matter of creating two separate virtual disks. There may also be options to select the boot drive in there.
Best of luck.