please never use the peter gutmann 35 pass method it is not and never has been required, it was a hypothetically secure method for deleting an unknown pre-IDE storage system that had unknown recording system and included patterns that should make erasure more complete based upon his hypothetical white paper that described hypothetical techniques to recover over written data from magnetic storage mechanisms. The techniques described to recover overwritten data does not work on modern drives at all so his multi-pass methods were and are unnecessary. Overwriting whole sectors/clusters with a single pass of zeros or pseudo-random bit patterns is more than enough and for large storage devices takes long enough as it is! Also note that overwriting a SSD with a single pass of zeros can, with certain manufacturers firmware, be treated as if one TRIMmed the SSD when TRIM command itself is not possible to send like when the SSD is in a USB enclosure and the SSD is not recognised as a SSD by windows OS.