On 3/7/2014 8:22 AM, michalpl7 wrote:
ddrescue -f -g -n /dev/sdb /dev/sda /mnt/rescue1.log
My first thought is wondering what you meant by the "-g", as that is not
a valid option. Depending on what you meant, it could affect the
accuracy of this reply.
1) Does ddrescue overwrite data on /dev/sda (target) if it can't get it ( bad
sectors ) from /dev/sdb or data from 1st run will remain on target drive?
No, ddrescue does not write data to the target if the read fails. So if
sector 100 had a read error on the source drive on the second run,
sector 100 on the target drive would still have whatever data was there
before the second run. So any data that was good after the first run
would still be good on the target.
2) Does ddrescue overwrite data on /dev/sda (target) if I didn't specify log
file from 1st run ( create new one )?
Yes, ddresuce will overwrite the data. But as long as it was the same
source and target, and since only good data is written, you will not
loose any good data that was written to the target on the first run, and
could possibly gain good data from the second run.
3) If answers to questions above are YES then I understand that it copy this
new run in same place ( sectors ) as 1st one so I can put it together in data
recovery application?
Maybe someone else can answer this better than me, but I don't see a
problem with continuing your rescue using the first log, since it was
finished as commanded. I am assuming you wish to continue without the -n
option to further the rescue. Did you also do a full run with the second
logfile?
If you really want to be technical and make sure you have the best of
both runs, there is a function in ddrescuelog where you can merge 2
logfiles, but I am not familiar enough to give any advice on that. See
the description below from the ddrescue manual.
'--or-logfile=file'
Perform a logical OR operation between the finished blocks in file
and those in logfile, and write the resulting logfile to standard
output. In other words, in the resulting logfile a block is shown
as finished if it was finished in either of the two input logfiles.
Scott
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