ASRock motherboard destroys Linux software RAID
I suspect what's actually happening here is there was an old GPT partition table on the disk which was not wiped before mdadm -C was run.  This means it has a correct primary partition table (with correct CRC etc), and MD RAID has overwritten the secondary PT at the end of the disk.<p>Unfortunately (and I genuinely hate to be "language lawyering" when someone has lost all their data), the ASRock firmware is doing the right thing according to the letter of the UEFI spec -- see section 5.3.2 of <a href="http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_7_A%20Sept%206.pdf" rel="nofollow">http://www.uefi.org/sites/default/files/resources/UEFI%20Spe...</a> :<p><i>> If the primary GPT is invalid, the backup GPT is used instead and it is located on the last logical block on the disk. If the backup GPT is valid it must be used to restore the primary GPT. If the primary GPT is valid and the backup GPT is invalid software must restore the backup GPT.</i><p>Good time to promote my videos visualizing how GPT and Linux RAID work :-)  I did some cool live visualizations of mdadm, mkfs.ext4, gdisk, injecting errors etc.  <a href="https://rwmj.wordpress.com/2018/11/26/nbdkit-fosdem-test-presentation/#content" rel="nofollow">https://rwmj.wordpress.com/2018/11/26/nbdkit-fosdem-test-pre...</a> <a href="https://rwmj.wordpress.com/2018/11/06/nbd-graphical-viewer-raid-5-edition/#content" rel="nofollow">https://rwmj.wordpress.com/2018/11/06/nbd-graphical-viewer-r...</a>