A few months ago I saw a local company performing thorough physical destruction of thousands of hard drives. Here’s a pic!
Thorough physical destruction of the entire data storage medium is generally considered the most certain way to counter data remanence. However, the process is generally time-consuming and cumbersome. Physical destruction may require extremely thorough methods, as even a small media fragment may contain large amounts of data.
Physically breaking the media apart, by grinding, shredding, etc: