On 5/19/2014 11:42 AM, Antonio Diaz Diaz wrote:
Even if all passes are made in the same direction, ddrescue will go
twice per pass over any area (unwanted or not) that is between rescue
domain extremes, because it must go back to the beginning to start the
next pass.
There is a way to make ddrescue perform the copy phase in just one
pass, and therefore in one direction; disable skipping with
'--skip-size=0'.
I for one am happy to see the ability to to turn off skipping in this
latest release. While ddrescue has what could be considered the best
"logical" algorithm for data recovery, sometimes it is not the best
"physical" thing for a disk. I think we would like to see and understand
whatever options would be needed to get ddrescue to go in a "strait
line" and "do what I say" when desired. I have not had much time lately,
but I was not too long ago doing some benchmarking with different
versions and options, and can say that I have seen some very nasty plots
of the head bouncing all over the place. I know one thing that helps is
to increase the logfile-size option. If I can ever find the time again,
I will do more testing. But I do agree that some of us would like more
control, and are sometimes unsure of how to properly use the options to
get it.
Antonio, I did just finally do a quick benchmark of 1.18-rc1 and do not
have any anomalies to report.
Scott
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