Re: [Bug-ddrescue] bug on non-hardbs rounded start position or size!

[Antonio Diaz Diaz]

Hello Dmitri,

Dmitri Kostin wrote:
> Hello! Thanks for your program!

You are welcome. :-)


> I have detected a bug. When using start or end positions that are not
> rounded to hardbs (512 bytes) - I always receive an error of "bad
> sector" with sizes varying from 0 to 512 bytes.
> [...]
> Oh! My HDD is such a slow one and contains many actual bads
> that I use only -d -c1 -n -N.

This is not a bug, just a limitation. From the manual:

http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Direct-disc-access
"NOTE! Sector size must be correctly set with the '--sector-size' option 
for this to work. Only whole sectors can be read; both 
'--input-position' and '--size' must be a multiple of sector size."

You can try binary prefixes. For example -s49Ki instead of -s49k.


> Also, my HDD being rescued contains areas with good
> read rate (about 4Mb/s) sized about 600M, and between them - areas of
> slow readable sectors (about 4 seconds per sector). I need some
> options to immediately skip such slow areas to recover as much as
> possible with minimal time spent. For example, such strategy as to
> read forwards until slowing to min_read_rate or detecting an error,
> then read backwards, until slowing or bad, too. Then divide the
> maximum sized untried block by half and repeat.

Such "divide and conquer" strategies have already been tried in past 
versions of ddrescue with bad results. They produce a lot of head 
movement and no not reduce the total rescue time. Sorry.


Best regards,
Antonio.