[ale] Extreme Practical Data Recovery (Part 2)

[Greg Freemyer]

On Wed, Jul 23, 2008 at 1:54 PM, Robert Reese~ <ale at sixit.com> wrote:
>> Modern ATA drives don't allow you under the hood, so spinrite has
>> limited things it can do fix a drive.
>
> And you've based this assessment on...?
>

I work with disk drives as a routine part of my job (Computer
Forensics) but I admit to not knowing the ATA spec. as intimately as
some might.

for instance I know that hdparm's releases in the last 6 months have
the best low level sector addressing capability I have seen.  (ie. you
can read and write a true sector including the checksum data that you
no access to via normal 512 byte sector i/o.)  You can now use hdparm
to perform fault injection into a specific drive sector to see how a
raid array etc. responds to failed read.

I really don't think there are any ATA commands that let you tweak the
positioning of the head, signal strength etc., or I think I would have
read about it by now.

ddrescue attempts to increase the likelihood of a succesfull data read
by doing tricks like reading the sectors in reverse order.  This is an
attempt to get the heads to move to a slightly different position than
if you do it in the normal forward order.  Supposidely it can help,
but if there were real mechanisms to control the head positioning,
this kind of trick would not have to be employed.

Greg
-- 
Greg Freemyer
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com