Ed, I've been told the same thing. I worked SBLC for the AF, and we were told that data could be recovered after up to 7 rewrites, and the methodology was based on signal strength analysis. I.E. You read the sector of a hard disk umpteen millions of times and get enough samples of it to determine what was written there last time, overwritten once, overwritten twice, etc, based on the signal degradation created by overwrite.
Our destruction procedures were based on these assumptions. We had to do massive overwrites and then physically take apart, scratch, and then bend old HDAs (3375/3380 drives) before they could go to DRMO for metal recycling. And the "new fangled" PC hard drives were degaussed, and then melted in an incinerator for good measure. I don't know how true the "recovery after x overwrites" is either, but this is what we were trained on, and the paranoid procedures we followed. I'd be interested to see what methodology is used to ensure the data is really gone from IBM hard drives today, particularly with these massive RAIDs we all seem to use! Gary Diehl MVS Support "The glass is neither half full or half empty; the engineer who designed the glass simply allowed for a 100% increase in fluid storage." -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Ed Gould Sent: Thursday, January 31, 2008 2:01 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Data Erasure Products On Jan 31, 2008, at 3:48 AM, SUBSCRIBE IBM-MAIN Niall wrote: > How about encrypting the volume in its entirety before deletion? > > I've been through the DR/deletion exercise a few times, and used an > in-house > utility to overwrite the disk. If available, however, would > encryption not > be a possible solution in that even if a shadow of the data were > left, it > should at least be in a format that is not readable? > > I ask because some sites may already have invested in an encryption > tool, > and it might be an imaginative use of an existing asset. > I vaguely remember a story here I cannot remember where I heard it (it may be an urban legend). *SUPPOSEDLY* the CIA (NSA??) was able to read a disk even after data has been written on it, even after 10 or 11 times. I have heard this but where? I do *NOT* know if this is true or not. Ed ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
