[effie]

Right, so one better write 2x or 10x drive capacity of random data to it.

[isotopp]

You should be running flash with self-encryption (and make sure you have a drive that implements that correctly).

To zap a drive you ask it to securely drop the self-encryption key. The data will still be there, but without the key it is indistinguishable from random noise.

[effie]

Well who has time and energy to verify that. Just overwrite it several times, or destroy the drive.