On 21/02/17 05:21, Phil Turmel wrote:

On 02/20/2017 03:45 PM, Wols Lists wrote:

quoted

But there's a request on the linux wiki program for someone to write a
utility program that takes a ddrescue log and flags the duff sectors as
"soft unreadable". That would mean that if you can recover 35 drives,
provided no stripe has lost two sectors across two drives, you wouldn't
lose any data.

If you want to try and write that utility? Or if you want to email me a
ddrescue log with a bunch of failed sectors, I'll have a go at writing
it myself :-)

Check out hdparm --make-bad-sector.  You can get what you are describing
by scripting that.  It's marked very dangerous, but I guess if one has
nothing to lose....

Wol and I have tic-tacced on that a couple of times. He suggested the 
idea and I proved the viability of it by testing hdparm in a RAID to do 
exactly that. Neither of us has had a chance to stitch it all together, 
but the preliminary tests indicate that would do *exactly* what was 
required.

Given the hdparm commands are completely reversible and non-permanent, 
*and* they are being executed on a destination of a ddrescue, there is 
pretty much no risk (as long as the underlying glue code to be written 
gets the sector numbers and offsets right).

Regards,
Brad