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Re: Help with ddrescue

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
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

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.

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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