disk scrubber for Linux?

[Michael ODonnell]

Anybody know of a disk-scrubber for Linux?  I'm talking
about an app (typically a low-priority background task)
that continuously reads your disks to detect bad blocks with
the hope that you can do something about them before the
situation becomes critical.  This is of particular interest
with mirrored disks because bad blocks can silently render
your supposedly fault-tolerant kit, um, less so...

I've teoma'd and vivisimo'd and dogpiled and lycos'd and
hotbotted and altavista'd, etc, but no joy.