OpenBSD softraid crypto boot
Boot install CD or bsd.rd. Either pick shell or escape to one by pressing ! during installation before getting to the disk setup part. Create new disk devices by running sh MAKEDEV in dev. Run fdisk and disklabel to create a RAID partition on the physical drive. Run bioctl with all the magic options to create the softraid drive.
bioctl -c C -l /dev/sd0a -r auto softraid0 Continue the installer and install to sd1. Magic.