(Resend: message didn't show, was my original message too big? Posted one of the output files to a website to see)
The point of RAID1 is to allow for continued uptime in a failure scenario. When I assemble servers with RAID1, I set up two HDDs to mirror each other, and test by booting from each drive individually to verify that it works. For the OS partitions, I use simple partitions and ext4 so it's as simple as possible.
Using the CentOS 7.6 installer (v 1810) I cannot get this test to pass in any way, with or without LVM. Using an older installer, it works fine (v 1611) and I am able to boot from either drive but as soon as I do a yum update then it fails.
I think this may be related or the same issue reported in "LVM failure after CentOS 7.6 upgrade" since that also involves booting from a degraded RAID1 array.
This is a terrible bug.
See below for some (hopefully) useful output while in recovery mode after a failed boot.
### output of fdisk -l
Disk /dev/sda: 500.1 GB, 500107862016 bytes, 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x000c1fd0
Device Boot Start End Blocks Id System /dev/sda1 2048 629409791 314703872 fd Linux raid autodetect /dev/sda2 * 629409792 839256063 104923136 fd Linux raid autodetect /dev/sda3 839256064 944179199 52461568 fd Linux raid autodetect /dev/sda4 944179200 976773119 16296960 5 Extended /dev/sda5 944181248 975654911 15736832 fd Linux raid autodetect
### output of cat /prod/mdstat Personalities : md126 : inactive sda5[0](S) 15727616 blocks super 1.2
md127 : inactive sda2[0](S) 104856576 blocks super 1.2
unused devices: <none>
### content of rdosreport.txt It's big; see http://chico.benjamindsmith.com/rdsosreport.txt