What are Reallocated sectors?
Answer
Disk drives typically have spare physical sectors in case some sectors become bad. The swapping of bad sectors with functioning ones are accomplished using a lookup table and these "remapped" sectors are known as reallocated sectors. The number of reallocated sectors is primarily used as a metric of the life expectancy of the drive - a drive which has any reallocations at all is significantly more likely to fail in the immediate months.