On 29 Aug 2010 at 3:16, Bruno Wolff III wrote: Date sent: Sun, 29 Aug 2010 03:16:28 -0500 From: Bruno Wolff III <bruno@xxxxxxxx> To: Marko Vojinovic <vvmarko@xxxxxxxxx> Subject: Re: Scrub free disk blocks Copies to: users@xxxxxxxxxxxxxxxxxxxxxxx Send reply to: Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx> <mailto:users- request@xxxxxxxxxxxxxxxxxxxxxxx?subject=unsubscribe> <mailto:users- request@xxxxxxxxxxxxxxxxxxxxxxx?subject=subscribe> > On Sun, Aug 29, 2010 at 07:46:49 +0100, > Marko Vojinovic <vvmarko@xxxxxxxxx> wrote: > > > > Starting from the premise that every hard disk has in principle limited > > capacity to store data, one can always fill it up completely, then rewrite it > > completely again. I see no way of the old data being recoverable, because this > > is in contradiction with the fact that the disk was filled up completely two > > times. The old data has to be destroyed in order to make room for new data. At > > least as far as I can understand it. > > At least at one time it was possible because the data is stored in a region > and when overwriting the region you don't hit the same spot every time. > With the right equipment you could see these areas and tell what data had > been written in that spot in the past. > > I have heard that with the current generation of disks this is no longer > practical. But practical is mostly defined by what your budget is; so if the > data is valuable enough, it is potentially recoverable. Recalling a presentation at Defcon 2006, the space between tracks would contain information that could determin what was there before a format operation. A DES level wipe required writing 7 different patterns to every sector to make this practically impossible. I don't do that level of wiping disk, but do use scripts to clear the unused space before doing disk/partition images. Makes a huge difference in the image size, since zeroed out sectors compress to almost nothing in the image file. Did an image of an 80GB disk after a full install of Fedora, and it made a 12GB image file. After clearing the image was only 2.5GB. > -- > users mailing list > users@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe or change subscription options: > https://admin.fedoraproject.org/mailman/listinfo/users > Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines +----------------------------------------------------------+ Michael D. Setzer II - Computer Science Instructor Guam Community College Computer Center mailto:mikes@xxxxxxxxxxxxxxxx mailto:msetzerii@xxxxxxxxx http://www.guam.net/home/mikes Guam - Where America's Day Begins G4L Disk Imaging Project maintainer http://sourceforge.net/projects/g4l/ +----------------------------------------------------------+ http://setiathome.berkeley.edu (Original) Number of Seti Units Returned: 19,471 Processing time: 32 years, 290 days, 12 hours, 58 minutes (Total Hours: 287,489) BOINC@HOME CREDITS SETI 9925545.785910 | EINSTEIN 4468268.520851 ROSETTA 2199349.596714 | ABC 2320812.078459 -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
