Implement component 'scrubbing' in RAIDframe.
RAIDframe (raid(4)) provides various RAID levels to NetBSD, but currently has no facilities for 'scrubbing' (checking) the components for read errors.
- implement a generic scrubbing routine that can be used by all RAID types
- implement RAID-level-specific code for component scrubbing
- add an option to raidctl (raidctl(8)) to allow the system to run the scrubbing as required
- update raidctl (raidctl(8)) documentation to reflect the new scrubbing capabilities, and discuss what scrubbing can and cannot do (benefits and limitations)
- Allow the user to select whether or not to attempt to 'repair' errors
- Actually attempt to repair errors