disk scrubber for Linux?

[Michael ODonnell]

All that sector/cylinder sparing/remapping magic is
wonderful but it won't save you if one disk of a RAID
pair has a bad block mapped to a file that's rarely
read.  If the other disk goes bad and you think,
"No problem, I'll just replace that bad disk" you're
buggered because the remaining disk has the bad block
and you won't know it until you go to read that file
when you're syncing the new disk.  Too late...