I am trying to install Centos 7 on a couple 4TB drives with software raid. In the Supermicro bios I set UEFI/BIOS boot mode to legacy. I am using the Centos 7 minimal install ISO flashed to a USB thumb drive. So I do custom drive layout something like this using sda and sdb. Create /boot as 512 MB XFS raid1 array. Create SWAP as 32 GB SWAP raid1 array. Create / on 3.xxx TB XFS raid1 array. I then get error. "Your BIOS-based system needs a special partition to boot from a GPT disk label. To countinue, please create a 1MiB 'biosboot' type partition." I cannot seem to create the biosboot partition so it is mirrored to both drives for redundancy. Any ideas how to do this? I want everything mirrored to both drives.