Re: Wiping a disk clean

[Kilgallen@SpamCop.net (Larry Kilgallen)]

In article <PRWHe.7695$0C.7190@newsread3.news.pas.earthlink.net>, Jeffrey Carter <spam@spam.com> writes:
> Larry Hazel wrote:
>> If I create a binary file, use sequential_io to write records of all 
>> ones until Use_Error is raised.  Then, delete the file and repeat with 
>> all zeros.
>> Will the unused portion of the disk be wiped clean so that no one could 
>> recover what was written there before?
> 
> Probably not. The US Govt requires 3 passes with specific patterns, and 
> the most exhaustive study of the issue indicates that different 
> approaches are required for different kinds of drives. For most modern 
> disks, several passes with random data will suffice. "Several" is 
> probably 5 or 6.
> 
> And that doesn't even get into the issues of whether Sequential_IO will 
> write on all the unused portion of the disk, much less the unused parts 
> of partially used sectors, and so on.

Or the formerly used parts of the disk that have been "revectored"
in response to hardware problems.

In summary, there is a large body of knowledge in this area that is
not at all specific to Ada.