[DanBC]

The ATA secure erase command is faster, and should be better than overwriting. Overwriting has potential for missing sectors marked as bad but Secure erase will get those.

Multiple over writes is pointless. There's the Gutmann stuff, but that's ancient and the 35 passes was for multiple drive controllers, if you didn't know what drive controller was being used.

But then sometimes you don't have to do what works, but what other people tell you. Thus, if you're working to a standard it doesn't matter if DOD specifications are actually more secure than a single secure erase, you do what the spec calls for. And if you have to persuade other people that the data is provably gone it's easiest to just grind the drives.