Writing a large amount of garbage bytes on the disk track makes the disk data unreadable and unrecoverable. In most cases, the hard disk can continue to be used without external tools, as long as the hard disk can read and write, you can use this method. The destruction process is slow. It usually takes 1 to 3 hours to complete the destruction of data on a hard disk. The DOD/3Pass standard takes more than 1 hour; the GUTMAN/7Pass standard takes more than 3 hours. The delivered document is an electronic version of the certificate of destruction.