On 8 June 2012 17:37, zMan <[email protected]> wrote: > On Fri, Jun 8, 2012 at 5:20 PM, McKown, John > <[email protected]>wrote: > >> If it were a single drive in a Raid 5 type configuration, I'd guess it >> would be totally impossible. But in a Raid 1 (mirrored), why not? Each >> drive contains the entire set of bits. But I don't know that for sure. It's >> just a SWAG. >> > > Yeah, the RAID level would matter a lot! The DS8000 doc I found says it > supports RAID 5, 6, and 10. All of those do some "spreading" (or striping, > in RAID 10), so I'd guess the short answer is "Not very practical", or at > least non-trivial. OTOH, if it's NSA working over a discarded drive from an > Al Qaeda DS8000...
I was asked a couple of years ago to help recover some data from a failed system -- failed as in unnoticed single drive failure followed by second drive failure and discovery that backups had not been performed correctly. :-( I spent quite some time browsing recovered data in an image file. So much of the text data was either immediately readable, or trivially decodable, that I didn't initially realize that what I was looking at was an image of a single drive from a failed RAID 5 array! RAID 5 and friends have a lot of XOR'd data, and it all depends what it's been XOR'd with. For example, XORing EBCDIC letters with EBCDIC blanks generally just changes the case, which usually leaves the meaning pretty clear. Certainly some data will be gone, but much data, and many text strings in particular will survive. I just sent a very dead SATA RAID drive from home off for warranty replacement, and I would have erased or damaged it if it wouldn't void the warranty. So for me avoiding the $100 or so replacement cost is worth the small risk of them being interested enough in my data to spend time recovering it. But I can't think there is a business case for any large company not to be shredding failed drives when they cost only a few hundred dollars a pop. Google has a video of what they do to theirs http://www.youtube.com/watch?&v=1SCZzgfdTBo&t=211 Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
