I have a X8DTN+ motherboard. I am using the onboard Intel RAID with six 500GB hard drives. I created a RAID5 volume with all six hard drives. The RAID volume does not show bootable and I don’t see the RAID volume in motherboard BIOS.
X8DTN+ has legacy BIOS. Legacy BIOS does not support bootable hard drive volume larger than 2TB. You need to create a partition that is smaller than 2TB on the RAID5 volume.