On 21 September 2010 19:12, Antonio Diaz Diaz
<address@hidden> wrote:
Hello Reon,
Reon Toerien wrote:
Is it possible to do a reverse image starting at the last block and jumping
further back when bad blocks are encountered until block zero is reached? In
other words everything works in reverse.
Currently not. When trimming backwards a block, ddrescue marks this block for later splitting as soon as the first bad sector is found.
Reading in reverse a sector at a time is very slow (less than 100kB/s. One month to read a 250GB disc). This is why ddrescue currently uses it only to trim bad blocks.
If not could it be added as a feature request?
Of course. :-)
Should help eliminate the read ahead cache on the drive where it reads 16MB
ahead in a area that has bad sectors.
I guess it won't be simple. Does reading in reverse help if the drive is dumb enough that it always tries to read ahead forgetting previous failures?
The cache is still used but only populated with what has already been read
What pass (copy, split, retry, all) would be more useful to run in reverse?
I'll leave that to you and the rest of the clever people over here :)
I am sure the wonderful people in this list will help find the most useful behaviour to implement in ddrescue 1.14. Thanks in advance for your feedback. :-)
I'm sure they will.
Regards,
Antonio.