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Re: Help with ddrescue



On Fri, 08 May 2015 14:48:47 -0400
Gary Dale <garydale@torfree.net> wrote:

> On 08/05/15 02:32 PM, German wrote:
> > On Fri, 08 May 2015 14:23:39 -0400
> > The Wanderer <wanderer@fastmail.fm> wrote:
> >
> >> On 05/08/2015 at 02:16 PM, German wrote:
> >>
> >>> On Fri, 08 May 2015 13:40:01 -0400 The Wanderer
> >>> <wanderer@fastmail.fm> wrote:
> >>>
> >>>> On 05/08/2015 at 01:20 PM, German wrote:
> >>>>> Thanks, but some clarification is needed. Now I have two drives,
> >>>>> failed and a spare. Both are 2TB in size. Failed drive probably
> >>>>> has 1.6 TB data I'd like to recover. It has only one partition I
> >>>>> suppose.
> >>>> That's bad.
> >>>>
> >>>> If the drive has only one partition, it probably has a single
> >>>> filesystem taking up all of its space.
> >>>>
> >>>> When you create a ddrescue image from that partition, the new
> >>>> image will take up _at least as much_ space as the original
> >>>> filesystem. That's not the 1.6TB of "used" space; it's the full
> >>>> 2TB of "total" space. (Plus however much space is taken up by
> >>>> the "index" file used by ddrescue while doing its work.)
> >>>>
> >>>> That means that if your two 2TB drives are actually the same
> >>>> size, the "good" one will not have enough space to store the
> >>>> image you need to rescue from the "bad" one.
> >>> Thanks Wanderer. So, I have no chances with two drives the same
> >>> capacity? Would you advise to wait when I can get more capacity
> >>> drive and only then to proceed as to save some head ache?
> >> Yes, that's what I'd do in your situation. A 2.5TB drive should be
> >> more than enough; that would also let you store the
> >> sdb_failed.ddrescuelog file on the same drive, if you need to, so
> >> you don't have to worry about finding space for it elsewhere.
> >>
> >>> Once again, thanks for such a complete instructions.
> >> I wouldn't call the directions I gave "complete"; there's a lot of
> >> details you'll still have to work out on your own, because they
> >> will depend on the exact details of your failure and the recovery
> >> process. Still, they should at least provide you a good starting
> >> point.
> >>
> >> Again, I would recommend that you install (and read the
> >> documentation for) myrescue, and consider using that instead of
> >> ddrescue. I've used both (as well as dd_rescue), but if memory
> >> serves I've had better results with myrescue.
> >>
> > Thanks so much. I wait when I can get a bigger drive. Have a
> > greatest day!
> >
> >
> I think Wanderer may be overstating the problem a little. If the two 
> drives are exactly the same size, you can use ddrescue to duplicate
> the failed drive onto the new drive (ddrescue if=/dev/sdb
> of=/dev/sdc). However this will limit you to recovering in place on
> new drive.

What will this duplication accomplish? What advantages if I am
duplicate? After I duplicate the drive, what are my next steps?
> 
> Hopefully the file system is repairable which will make this
> possible. If the file system isn't, you need a third drive to hold
> recovered files.
> 
> 


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