[Bug-ddrescue] R: Re: DDRESCUE examples in the GNU website + 1 kind question

[gini . robert]

I mean that those drives hangs linux too.

Basically, skipping the BIOS would help a lot.

But in the mean time I suppose ddrescue would become like a standalone tool. As 
a matter of fact, it would need a special system boot.

About skip forward, I can say that ddrescue with -n option lasted too much time 
on bad areas with a disk I recently had at home.

I've run a windows tool that allows to run direclty in reverse mode.
Yes, it is slower, but it read straightly over 75% of the drive.

It is a several approaches. Needed to get very quickly an idea about the damage.

You know bad drives are going worst and worst if used too much.

Thank you
Roberto

------Messaggio originale------
Da: Antonio Diaz Diaz
A:Roberto Gini
Cc:address@hidden
Oggetto: Re: [Bug-ddrescue] DDRESCUE examples in the GNU website + 1 kind 
question
Inviato: 7 Ott 2011 18:17

Hello Roberto,

Roberto Gini wrote:
> thank you so much for your work with ddrescue.

You are welcome. :-)


> why don't you add a specific example and sequence for the case "cloning a
> drive with a lot of bad sectors" ?

Ddrescue can manage any number of bad sectors without special options. 
Of course an experienced user can shorten rescue time, but it depends on 
the drive's behaviour and I don't think any single example can cover all 
cases.

BTW, have you looked at the example shown here 
http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Algorithm


> Additionally, I'd like to ask you why don't to implement a user definable 
> *skip
> ahead size amount* *and read backward* , in case of bad sectors
> encountering.

Ddrescue already skips ahead an exponentially growing amount depending 
on rate and error history. It totaly skips an unreadable 1.44 MB floppy 
in 8 seconds. I don't think the skip value needs to be made any larger.

Reading backwards is much slower than reading forwards. So jumps should 
not be too large, and all trimming is best done in a second pass.


> P.S. there are some drives that are recognized nice by the BIOS, they do not
> make bad noises but as soon linux or windows starts effectively to boot,
> such drives (either if connected on secondary channels) hangs the windows
> boot. It would be nice to have a ddrescue like tool interfacing directly
> with the ATA interface. Do you know something similar out there? Have you
> ever thought about this?

As far as I know, ddrescue doesn't run on windows so, as long as the 
drive does not hang the linux boot, this is not a problem. About using 
interfaces directly, I have already decided not to do it.


Best regards,
Antonio.


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