[excivaamome]

The superblock is a logical construct of the file system. SpinRite doesn't care if it is looking at a super block or user data block. In fact SpinRite is file system agnostic, and can even be run on unformatted drives.

SpinRite works on a sector by sector approach. As each physical sector on the platter has it's own error correcting code, SpinRite will try to read damaged sectors multiple times (and multiple ways) to try and recover the data. SpinRite also has it's own advanced error correcting algorithms which it employs when the sectors can not be fully read. When a damaged sector is successfully read (or SpinRite determines it can't be read) the recovered data is moved to a new sector and the original marked as bad. Even if the sector can not be fully recovered SpinRite can usually read most of the data, recovering what it can rather than discarding the entire sector.

Most file system duplication programs work on either a file by file copy procedure, or preferably a block by block procedure. Even when a block by block approach is employed it should be remembered that the block is a file system abstraction, and each block can span multiple physical sectors. This approach can leave a large amount of otherwise readable data discarded when a bad block is encountered.

It's worth having a read about how SpinRite works
http://www.grc.com/files/technote.pdf