I have just upgraded from 3.X to 4.X, and my first boot failed with ``bad sector table not supported''
FreeBSD 3.X and earlier supported bad144, which automatically remapped bad blocks. FreeBSD 4.X and later do not support this, as modern IDE drives include this functionality. See this question for more information.
To fix this after an upgrade, you need to physically place the drive in a working system and use disklabel(8) as discussed in the following questions.
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