Gutmann&#x27;s paper talks about a time when you didn&#x27;t know what drive controller was used, and so he created a set of patterns to be used for each pattern.  That comes to (about) 35 different patterns.<p>This gets misunderstood as &quot;you need to do 35 passes of these patterns&quot;.  You don&#x27;t, Gutmann recommends a couple of overwrites of random data, and a single overwrite of zeros is probably enough.