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

[Scott D]

> This sounds like a bad head. If the slow sectors are unreadable 
> (errors) then you can adjust the skip size. With ddrescue 1.19 you 
> could add the option --skip-size=25Mi,50Mi (if I have the format 
> correct). That will skip 25MB on the first error, with no more than 
> 50MB skipped on each consecutive error. This will skip out of the bad 
> head faster than normal and allow more reading of the good data first. 
> If the disk has 2 platters then it has 4 heads, and 600MB of good read 
> would be 3 heads of 200MB chunks, and a bad head of 200MB. This is an 
> estimate without knowing what drive you actually have or the number of 
> platters. So in theory the added option would skip out of the bad 
> chunk after no more than 8 errors. On the reverse pass any trailing 
> data that was skipped is picked up. I have bench tested this method 
> and it has good results. Head movement is linear, and the data from 
> the good heads is recovered much faster. Once it gets past the copying 
> phases and starts the trimming phase and scraping phase expect it to 
> be much slower as it is dealing with the bad head, and other than 
> being patient and waiting for the recovery to finish (or the drive to 
> die), the only other option is take it to a professional. 
I forgot that there are 3 passes with ddrescue 1.19. The 3rd pass is 
without skipping and will also be slow. With the correct options and 
skip size, the first 2 passes (forward and then reverse) are the 
important ones to get the data from the good heads.

Scott