While I was testing the cloning and resizing of the user data file system, I came across one drive which FreeBSD was inexplicably unable to access again after the PS3 had mounted it. I knew the file system was good, because the PS3 was still able to use it and I could mount it read-only under Linux, but any attempts to access it via FreeBSD resulted in a UFS2 superblock error:
UFS2 superblock failed: fs->fs_fsbtodb (0) != ILOG2(fs->fs_fsize / sectorsize) (3)
Testing the drive further, I confirmed the same thing happened when the drive was natively formatted by the PS3; FreeBSD was still unable to access it. So this wasn't an issue being introduced by cloning or resizing the file system.
What was going wrong? What was different about this drive?