Looking at the sd driver, it seems like it does sector remapping.

The existance of sd_reassign_blocks() does not indicate that it either
works or is called by anything.

In reality, this should probably be done by a user-level utility like
Sun's `format', but nobody has written one.

   Also, what happened to ncheck and icheck?

They were based on AT&T code, and have not been rewritten yet.