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Re: [Bug-ddrescue] --input-position and --min-read-rate parameters ignor

From: Robert Backhaus
Subject: Re: [Bug-ddrescue] --input-position and --min-read-rate parameters ignored
Date: Tue, 17 Jun 2014 08:56:18 +1000

On 16 June 2014 18:55, <address@hidden> wrote:

> Hello,
> - i : --input-position : starting position in input file
> This parameter is buggy : it is taken into account only when its value
> is larger than the current input position. If one want to use an offset
> that is smaller than the current position, one first have to the value
> for "-i" near the end of the drive in order to finish the cloning. Then
> only, we can start the cloning again with a smaller "-i" value.

No, this is the correct operation of -i, and it is not ignored. If you
specify -i, ddrescue will not attempt any rescues before that value. It
will not jump back and start trimming bad blocks or reading in a different
location immediately. This is by design.

> -a / --min-read-rate : Minimum read rate of good areas in bytes/s
> I tried setting it to "-a 20000", but I still oberve very slow reading
> rates, sometimes of only 256 B/s.
> I hoped that setting "-a" would help speeding up ddrescue and clone the
> easier areas first.
> But after several passes, the software is trimming failed blocks and the
> speed is much slower than thus set by "-a".
> I'm not sure if the value of "-a" is ignored or if there is something
> that I did not understand.

-a cannot prevent slow reads from happening. When there is a slow read, it
considers it as an error and jumps to another location to find data it can
retrieve faster. Blocks skipped because they are slow are then read before
the trimming stage, and -a is not considered during trimming, as slow reads
and errors are expected then. This is outlined in the info file for

> Regards,
> Julien
> --
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