Mr. RAID ... ... well ... really?
Anyway ... relocating the sector can help, but if SMART or better the hdd-controler does not detect the media-error himself, then you'l have a bigger problem. Theoretically should do the controler remap this sector "transparently" ...
I know an article, which descripes the procedure to "remap" an sector within an mdraid-array, but i can't remember and i have currently to less time to google-fu that by myself ... sry.