Google tracks the location and status of each hard drive in its data centers.
If there is a problem with a hard drive, it's reformatted and retested. If the drive does not pass these tests it's then removed, and the data on the drive is overwritten and verified to make sure it contains no customer data.
Photo credit: Google/YouTube.com
Sonja Thompson has worked for TechRepublic since October of 1999. She is currently a Senior Editor and the host of the several blogs.