Description of problem:

This is somehow a continuation of BZ #2152092.

We have customers trying to install a SoftRaid made of the whole disks.
On UEFI, this requires using 1.0 metadata so that the firmware sees the UEFI partition created on top of the SoftRaid.
In BIOS mode, there is no special requirement, except on PPC64le where 1.0 metadata has to be used as well to see the PREP partition.

The issue with all this is there is no way to tell the GUI to create such SoftRaid.
The only possibility is to use the command line, e.g.:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

1. mdadm --create /dev/md0 --level raid1 --metadata=1.0 --raid-disks=2 /dev/vda /dev/vdb
   • • • • • • • 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

When doing so, a re-scan of the disks in the GUI shows the array and we can build partitions on this [1].

But actually, it's more complicated, because for some reason, a re-scan isn't enough.
Once the SoftRaid has been created, we need to tear it DOWN then UP again, otherwise Anaconda doesn't see the SoftRaid but no disk at all.

See screenshots attached:

1. "Rescan just after creating the Raid.png" (no disk seen anymore)

At this step, I restart the Raid:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

1. mdadm --stop /dev/md0
   mdadm: stopped /dev/md0

1. mdadm --assemble --scan
   mdadm: /dev/md/0 has been started with 2 drives.
   • • • • • • • 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

2. "Rescan after restarting the Raid again.png" (MDRAID set (mirror) seen)

[1] On PPC64le this doesn't work, because Anaconda complains about the PREP partition not being valid for bootloader ("No usable boot drive was found"), which is somehow not true (it boots fine when creating the partition using the command-line prior to configuring using the GUI).

Version-Release number of selected component (if applicable):

anaconda-33.16.7.12-1.el8

How reproducible:

Always

Steps to Reproduce:

1. Create a VM with 2 disks

2. Start the installer

Actual results:

No way to create a "MDRAID set"

Expected results:

Some easy way to create a "MDRAID set"