Comment 13 for bug 1543221

what actually happens:

1) nailgun-agent reported 2 disks. /dev/sda (3T) and /dev/sdb (1G)
2) fuel-agent wiped out the beginning and the end of all disks. So, disks became clean and without any partition table
2) fuel-agent chose to put /boot partition and bootloader only onto smaller than 2T disks if possible due to https://bugs.launchpad.net/fuel/+bug/1461126 , so, /boot was created on /dev/sdb
3) fuel-agent finished provisioning without errors and astute rebooted a node.
4) during loading, node tried to boot from disks (but only 1 disk was available) - /dev/sda. /dev/dsb where bootloader and /boot partition were written, wasn't available at the early stage of booting.
5) /dev/sda didn't have any bootloader code, so BIOS/UEFI tried to boot from invalid (in term of operationing) boot sector and threw Illegal OpCode at red screen of death.