Re: dd for failing discs?

[Pádraig Brady]

On 02/12/2014 08:08 AM, Bernhard Voelker wrote:
> In various mailing list threads about failing discs like [1],
> the advices for trying to rescue as much data as possible
> always mention gnu_ddrescue, ddrescue or dd_rescue, and
> often claim that plain dd is a bad choice (not in this
> case).
> 
> [1] http://lists.opensuse.org/opensuse/2014-02/msg00424.html
> 
> Would it really be that bad to use something like the following?
> 
>   dd if=/dev/sda1 of=sda1.img conv=noerror iflag=fullblock
> 
> If this is true, we could add a link like
>   http://www.gnu.org/software/ddrescue/
> into the Texinfo manual, otherwise, we should add an example
> like the above.

This was discussed in http://bugs.gnu.org/6667
You would need conv=sync to pad out the unreadable parts.
The example from there would be useful in the docs.

> (AFAIK tools like ddrescue try an adaptive approach for
> 'ibs' values on failing sectors, and have other sophisticated
> features like backup merging - admitted.)

Right, so would be good to mention along with the example.

thanks,
Pádraig.