I have already tried on Fedora forum. Mayby here I will find the answer
I have created new array in that way:
mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2
Now, I would like to add second partition to this array, but every time I do it via this command:
mdadm --add /dev/md0 /dev/sdc1
I receive: "faulty spare" when I check array's condition via mdadm --detail
These partitions are exactly the same. I have even tried with other HDD but the same model with, again, the same partitions configuration. Again, added partition becomes "faulty spare".
When I create array using these two partitons instead of adding one of them later, everything goes fine.
What is going on? Could you help me?