Parsnip

I ended up just going with the parity rebuild for both drives.

Before I started rebuilding it from parity, it did load in Unassigned Devices, and I was able to browse and spot-check the contents to confirm that files were accessible. There was only one partition listed under UD (still xfs) and nothing seemed out of the ordinary, but I understand what you're saying about the USB bridge potentially being the cause of the issue.

I've tried several things, such as repair_xfs and using testdisk to fix the filesystem, but it didn't seem to help. I ended up removing the drive from the array, starting the array, stopping it and then re-adding the drive. It is now rebuilding from parity. I plan to do the final drive after that is completed, but would love any advice on how to avoid this issue next time and not have to rebuild. They are the exact same model of external drive, so I expect similar issues.

Today I started the process of moving some external USB drives from their enclosures into the case for my Unraid machine. I have two 12TB WD Elements drives and one 14TB WD EasyStore drive. I started with the EasyStore. The installation went fine, and the drive showed up when I started the machine, though the reported serial number for the drive changed. I created a new array configuration and marked the parity as valid, and everything worked perfectly upon starting the array. I then moved on to repeat the process with one of the Elements drives. Installation and startup went the same, also showing a different serial number. I repeated the process of creating a new array configuration and marking parity as valid. This also seemed to go correctly, at least until I started the array. Then it showed the newly-moved drive with a FS of 'auto' (previously 'xfs') and said 'Unmountable: Unsupported partition layout'. I tried stopping the array and setting the disk's FS to xfs, but that didn't fix the issue. The Fix Common Problems scan suggested starting the array in maintenance mode and running the filesystem check, which I did, but it still didn't fix the issue. I'm now stuck wondering what the safe way to proceed is. Ideally I could get this drive (and the remaining Elements drive) into the array without rebuilding from parity, but at this moment I'm very concerned about losing data if I proceed without guidance. Thanks!