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On 9 Jan 2010, at 09:23, Neil Bothwick wrote: |
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> On Sat, 9 Jan 2010 07:20:18 +0000, Valmor de Almeida wrote: |
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> |
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>> Sometimes the "current rate" reads 0 B/s for a long time... and "time |
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>> from last successful read" can be 8m. |
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>> |
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>> Would any one know whether this is normal? |
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> |
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> Doesn't ddrescue retry on blocks it cannot read? That would explain |
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> the |
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> variable read rate, even the period of zero activity. If your drive is |
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> that badly damaged, dd would have been no use anyway. |
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I think Valmor is using GNU ddrescue, with which one makes the |
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multiple passes manually. The "-n" flag on the command line that |
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Valmor posted (`ddrescue -n /dev/sda /dev/sdc rescued.log`) relates to |
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the examples given in the GNU manual page [1]. I believe that GNU |
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ddrescue is the better version - it was inspired by garloff's original |
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work, and makes improvements, but it operates differently. |
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Having said that, it could just be that the drive _firmware) is making |
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multiple attempts to read the failing blocks before returning the |
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failure (or the data, in the case that a 2nd attempt to read the drive |
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was successful) to the host o/s. Isn't this how hard-drives work? |
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ddrescue worked fast here when I tried it here recently on a drive |
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with only one unreadable block, but Valmor's drive is failing much |
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more severely. TBH, I would expect reads from a badly-failing drive, |
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but this is an intuitive expectation, not a reasoned one. I think the |
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best thing he can do is hold his breath, wait until its finished and |
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see how if the results are readable, after running `fsck` on the |
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mounted filesystem. |
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Valmor: when I ran the `ddrescue -dr3` stage I had no success at all, |
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however the system was fine after a reboot & a `chkdsk`. Better than |
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it had been, in fact, on the old hard-drive. You might have more luck |
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getting *some* of the blocks showing as failed when you run it on your |
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drive, but don't be too disheartened if you don't. |
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Stroller. |
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[1] http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html#Examples |
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