Re: [Bug-ddrescue] On the reading of slow areas (option introduced in 1.15pre2)

[Antonio Diaz Diaz]

Hello Gábor,

Gábor KATONA wrote:
> If I noticed it correctly, than all areas which fall below the given 
> threshold gets marked with *, meaning failed block non-trimmed.

Not exactly. Slow areas are indeed read correctly, so they are marked as 
'+' (finished). If the read rate of such a correctly read area falls 
below the --min-read-rate, ddrescue will then skip ahead a variable 
amount depending on rate and error history. This skipped area will be 
marked as '*' (non-trimmed).


> If I understand the algorithm correctly, these blocks will not be read on a 
> subsequent run with a -n option, but only when we turn to splitting.

The areas marked as non-trimmed are tried before splitting. So they are 
tried in a run with the -n option. The problem is you can run ddrescue 
only once with the "-n" or "--min-read-rate" options. The second time 
you use the "-n" option, ddrescue does nothing because only non-split 
and bad-block areas are left. The second time you use the 
"--min-read-rate" option, it has no effect because no more non-tried 
areas are left.


> If this is correct, I would suggest to have a new logfile status 
> character meaning "slow block", and have a new option meaning "try again 
> slow blocks". This way slow blocks would not be marked as bad blocks, 
> and they could be saved before turning to the most difficult parts, but 
> only after the most healthy blocks are saved.

I guess you mean "marking differently blocks skipped after finding a 
slow area from those skipped after finding an unreadable area". This 
could be useful, but is a major change to the current algorithm. I'll 
think about it. Feedback is welcome. :-)


Best regards,
Antonio.