When we want to make GPT the default partitioning, we must ensure the installability of a software raid as well. At the same time, we must continue to maintain the availability of a software raid even with MBR (DOS) partitioning.

Testcase 1: GPT

1. Provide a BiosBoot system with 2 connected hard disks
2. Delete any existing partition table on all hard disks by overwriting the first mbs
   [...]# dd if=/dev/zero of=/dev/sd[a|b|c] status=progress
3. Boot the installation disk, select the first installation option (w/o media check) and press <tab> to access the kernel command line. At the end add "inst.gpt" (w/o the ") and press <enter> to start the installation
4. Select "Installation Destination", tick all (at least 2) harddisks, and custom storage configuration. Select "DONE"
5. The partitioning form opens. Tick the "+" sign and a form "Add a new Mount Point" opens
   1. select /boot as the mount point
   2. enter 1 Gib as size
   3. Tick "Add Mount Point"
      A new mount point is created on sda1
6. The "Device Type" is shown as "Standard Partition"
   1. Modify to RAID and select appropriate RAID level (e.g. 1)
   2. update settings
      Device on the left column changes from sda1 to "boot" (beyond "New Fedora x installation")
7. Use the "+" sign to add another Moint Point
   1. select / as the mount point
   2. enter 15 Gib as size (the same as a default installation would choose)
   3. Tick "Add Mount Point"
      You find a new moint point of device type LVM, a VG fedoara_fedora of the exact size you entered above
8. Modify Volume Group
   1. Select Raid level RAID1 (or according to your number of disks)
   2. leave size policy on "Automatic"
   3. update the choices
      On the left side you find a device "fedora_fedora:root
9. select DONE
   1. You get a message you need a special partition biosboot on a GPT system
   2. Close gets you back to configuration screen
   3. use the "+" sign as above to add a partition of type biosboot and size of 1 MiB ad advised in the message
   4. Anaconda creates a biosboot as the first partition (sda1)
   5. try to change Device Type to RIAD, it is always reset to sda1 as soon as you select " update settings".
10. select DONE again, you get a list of partitioning tasks the system is about to perform, sda with 3 partitions, all other with 2
11. Begin installation

Expected result
1. Anaconda should install a biosboot partition on all disks included in the boot raid.
2. The system should continue to boot with any one of the disks broken (removed), specifically w/o the original start disk (sda).
3. The system will remain bootable even if any single of the RAID member disks is defective.

Testcase 2: MBR

1. Provide a BiosBoot system with 2 connected hard disks
2. Ensure every disk contains a (empty) MBR (DOS) partition label
3. Boot the installation disk, select the first installation option (w/o media check) to start the installation
4. Select "Installation Destination", tick all (at least 2) harddisks, and custom storage configuration. Select "DONE"
5. The partitioning form opens. Tick the "+" sign and a form "Add a new Moint Point" opens
   1. select /boot as the mount point
   2. enter 1 GiB as size
   3. Tick "Add Mount Point"
      A new mount point is created on sda1
6. The "Device Type" is shown as "Standard Partition"
   1. Modify to RAID and select appropriate RAID level (e.g. 1)
   2. update settings
      Device on the left column changes from sda1 to "boot" (beyond "New Fedora x installation")
7. Use the "+" sign to add another Moint Point
   1. select / as the mount point
   2. enter 15 Gib as size (the same as a default installation would choose)
   3. Tick "Add Mount Point"
      You find a new moint point of device type LVM, a VG fedoara_fedora of the exact size you entered above
8. Modify Volume Group
   1. Select Raid level RAID1 (or according to your number of disks)
   2. leave size policy on "Automatic"
   3. update the choices
      On the left side you find a device "fedora_fedora:root
9. select DONE
   you get a list of partitioning tasks the system is about to perform
10. Begin installation

Expected result
1. Anaconda should install a MBR record on all disks included in the boot raid (check log file).
2. The system should continue to boot with any one of the disks broken (removed), specifically w/o the original start disk (sda).
3. The system will remain bootable even if any single of the RAID member disks is defective.

Addendum
The actual test results are described in a comment further down!
(Comment 6)