Re: [Bug-ddrescue] GNU ddrescue 1.18-pre3 new option complication

[Scott Dwyer]

I have a theory on it, at least to try to automate it. From what I have 
seen, when the slowdown happens, the speed drops by half. And I have 
also seen it drop again by half, so down to 25% from original read 
speed. So if you can get the fastest average read speed (over a few 
seconds at least) that has occurred so far during the current operation, 
then set the reopen speed at say 60% of that, and after a few 
consecutive periods of below the 60%, perform the reopen.

Scott

On 8/25/2013 6:54 PM, Antonio Diaz Diaz wrote:
> Scott D wrote:
> > Might have found a sligh flaw with the "-O" option idea. The flaw is 
> > that it does not take an actual error (at least not one that ddrescue 
> > sees) to cause the slowdown. If there are difficult spots on the disk 
> > but no reported errors, it can still cause the reads afterwards to 
> > reduce speed.
>
> If it helps, it is certainly possible to make ddrescue reopen the file 
> after one or more slow reads.
>
> Of course I would prefer to see the kernel fixed, or at least a 
> explanation of why it slows down after an error.
>
>
> Best regards,
> Antonio.
>
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