I think you missed my point
In this particular thread, the discussion is NOT about Tape versus Disks. I'm simply commenting on the comment that it would be "better" to rely on the obscurity of tapes for security than rely on encryption on disks. I'm saying that there is no substitute for encryption in security and that obscurity doesn't cut it.
Yes you can encrypt data on both tape and disks. But that isn't what I was responding to.