Hello RJ and others,

On 27/01/2024 at 00:45, RJ Marquette wrote:

Quick follow up:  When I rebooted, the partition tables got munged
again.  Definitely a BIOS issue.

Today I came across a similar issue with a RAID1 array of two 
unpartitioned drives where the RAID superblock on one drive was 
overwritten with a GPT partition table at every boot, but the superblock 
on the other drive was not affected.

It turns out that the affected drive had remnants of a GPT partition 
table (protective MBR at the beginning of the drive and secondary GPT 
header and table at the end of the drive), whereas the unaffected drive 
did not.

After deleting the secondary GPT header and protective MBR with wipefs, 
the RAID superblock was not overwritten any more. So it seems that 
something, presumably the BIOS/UEFI firmware, found the secondary GPT 
table on the drive and decided to "restore" the missing primary GPT table.