&gt;A few passes of pseudo random data is probably better if you need to persuade other people that the data has gone.<p>You only need one.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Data_erasure#Number_of_overwrites_needed" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Data_erasure#Number_of_overwri...</a>