This is what NIST says about it[1]: Advancing technology has created a situation that has altered previously held best practices regarding magnetic dis

This is what NIST says about it[1]: Advancing technology has created a situation that has altered previously held best practices regarding magnetic disk type storage media. Basically the change in track density and the related changes in the storage medium have created a situation where the acts of clearing and purging the media have converged. That is, for ATA disk drives manufactured after 2001 (over 15 GB) clearing by overwriting the media once is adequate to protect the media from both keyboard and laboratory attack. That's an elaborate way of saying that zeroing a healthy modern disk is sufficient. No need to break out the crucible or jackhammers. If you really need to indulge your paranoia then use some wiping system that does multiple overwrites with random data. It's not necessary, but at least you won't put your eye out. [1] http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-88.pdf http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublic... If the device isn't healthy and can't zero all of the media then you will need to resort to physical destruction.