Re: [Bug-ddrescue] A way to check if ddrescue did a good job?

[James Wilson]

Hi Theo,

A quick query - if this disk was part of a RAID5 array, the should cater for a 
single disk failure.  Your array will be degraded, but still functioning with 
no loss of data.

Replace the failed disk with one of the same capacity, and it should rebuild.  
Or is this not the case?

Regards,

James

On 25 May 2012, at 14:17, Théo Koelz wrote:

> Hello,
> 
> Again not a bug, just a question (and maybe a suggestion). Ddrescue now
> claims to have successfully rescued my hard drive, awesome, but a few
> strange things happened and that makes me doubtful : I was rescuing a
> 1TB HDD, the first 400GB went smoothly, it was pretty fast with few
> errors, from 400GB to 420GB it went extremely slow (a few hundred B/s at
> worst and only a few thousands on average) and then the disk must have
> failed : it wasn't here anymore according to Disk Utility and DDrescue
> was going over the 500+ GB left to rescue in seconds (over and over ad
> infinitum it seemed, but there was no disk activity according to the
> motherboard), I then rebooted and the disk was back, I launched DDrescue
> again and after not long the disk must have failed again since DDrescue
> flagged more than 500GB as bad sectors, I rebooted again and started to
> rescue the bad sectors (ddrescue -d -f -r3 ...) and surprisingly things
> went smoothly and it was done in like 2 days with only a small bad
> sector of 452608B that couldn't be recovered (my source disk is now
> flagged as imminent failure though).
> 
> Maybe everything is well and I've been lucky, but as I said I'm a bit
> doubtful and would like to know if there's a way to check if ddrescue
> did a good job or not (my disk was part of a raid 5 so I can't do this
> the obvious way, of course I could try to do a raid recovery and see how
> it goes but I can't do this before a few days and anyway, in the mean
> time, I would prefer to check before hand if the disk was rescued
> successfully or not...). I didn't read anything about this in the manual
> so I don't know if ddrescue can do that, but it would be useful (one way
> to check this quickly could be to select a few random places on both
> disks and compare them, but maybe some other software already does
> that?).
> 
> As usual thanks in advance, you've been very helpful.
> 
> TK
> 
> 
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