> -----Original Message----- > From: tclug-list-bounces at mn-linux.org > [mailto:tclug-list-bounces at mn-linux.org]On Behalf Of Jonah > Sent: Friday, October 01, 2010 3:27 PM > To: tclug-list at mn-linux.org > Subject: Re: [tclug-list] Hidden hard drive partitions > > > I am not as proficient as I am sure most of you are in the mechanics > and science of data layout and retrieval on hard drives. > > I have used Ontrack for a variety of times to retrieve data and > assumed it was from raw scraping for data that had lost the pointers. > When the drive had been formatted, I sometimes still had success in > getting data off. > > I one time took a training session for a SAN environment with EMC, and > a number of DEA agents were there as well also attending the classes. > Afterwards, we hit the pub and they told me they can retrieve data up > to 37 layers of writes. Now, that may not mean anything without the > documented who/how/show-me details around here, but I can't imagine a > DEA agent to arbitrarily lie about such details when I am beating him > in billiards. > > I asked what application he uses but he only told me it goes on > measuring layers of degraded information left on the drive. He > wouldn't tell me more. > > For what its worth.... > The error-detection-and-correction coding that accompanies all data recorded helps this immensely. Various types and layers of coding allow correct data recovery in the presence of dropouts and gaps from various defects or "phenomena". The process must start with getting the "raw bits" off the platters using analog signal enhancement and encryption techniques. There are umpteen layers of encoding (with correction techniques) before one gets to "normal" file header and segment levels that have their own sector tables and correction schemes. Hardware and firmware built into the drive normally does all this for us so we only see the "simple stuff". Much is doable, but I have no idea whether that 37 layers of recovery is usual or "we did that once". Chuck > > > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org > http://mailman.mn-linux.org/mailman/listinfo/tclug-list >