Which of the following is the MOST secure to erase data before disposal of server hard drives?

A 'hard wipe' (overwrite) leaves the physical media intact and can potentially be defeated by advanced forensic recovery techniques depending on the number of passes and drive type.

Reformatting only rewrites file system structures and does not overwrite actual data sectors, making the original data easily recoverable with common tools.

Degaussing works by applying an intense magnetic field that collapses the oriented magnetic patterns representing data on platters, rendering the drive unreadable by any means including forensic analysis. Unlike software-based methods, it is a physical destruction process that cannot be reversed or bypassed. NIST SP 800-88 recognizes degaussing as an approved sanitization method for magnetic media prior to disposal.

Deleting partitions removes the partition table entries but leaves the underlying data physically intact and trivially recoverable with forensic software.