Dave Howorth wrote:
Greg Freemyer wrote:
On Wed, Mar 26, 2008 at 11:33 PM, Sam Clemens <clemens.sam1@gmail.com> wrote:
You would be amazed at what can be accomplished with scanning electron microscopes (due to the fact that the path of an electron is effected by magnetic fields.). From what I understand, due to hysteresis effects, a track starts out at 'full width', but each time a magnetic field is reversed, a "tail" is left on each side. Apparently, these residual fields can be used to reconstruct data which was previously overwritten. I would love a true reference (from the last 15 years). I have spent many hours looking into the question. The best I have seen is people claiming they can recover a bit here and bit there from modern drives. Not even any full bytes.
I have a NIST document that says labratory based recovery of data is impossible for disk drives 20GB or larger if the have been overwritten with a single pass of data. ie. Any data including all zeros.
It is certainly possible to read magnetic domain information from surfaces using an AFM (atomic force microscope) in Magnetic Force Mode (MFM). I've done that but not with a hard disk. If you google with those keywords you can find images showing what can be seen - e.g. left over data down the edge of tracks. But I don't know when those images were made or what's possible or not with current hard disks.
I don't know about any equivalent SEM techniques.
My understanding is that any method which has fine enough resolution to show the reversals of the magnetic domains is sufficient. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org