2.3.4 -> 2.4.0 GEOM complains about disklabel, then mountroot doesn't

[Fish in a Barrel]

After upgrading, I get an invalid disklabel error when my mirror is launched:

GEOM: mirror/pfSenseMirror: invalid disklabel

mountroot subsequently fails with error 19.

Mounting from ufs:/dev/mirror/pfSenseMirrors1a failed with error 19.

Here's a screenshot: https://i.imgur.com/4Zzvait.jpg
If I reboot with kernel.old, everything comes up just fine.

Any idea how I fix this?

[jimp]

Your safest bet is to reinstall. But I would test those drives, first. The upgrade wouldn't (and couldn't) touch the disk layout. Newer versions of FreeBSD are generally better at identifying and preventing disk problems from compounding themselves, so maybe there actually is some aspect of the label that is invalid.

I don't know if it will work for that particular error, but you can try setting this in /boot/loader.conf.local:

kern.geom.part.check_integrity=0