Re: [Bug-ddrescue] help needed recovering a hard drive with bad blocks

[Ariel]

On Tue, 17 Apr 2007, gr wrote:

> 1.  Format new drive using 'dd if=/dev/zero
> of=/dev/newdrive'

Not necessary.

> 2.  Use ddrescue to make image as fast as possible:
> ddrescue -B -n /dev/baddrive /dev/newdrive
> /media/usbflashdrive/logfile

Close, but you forgot about partitions.

I'm assuming the old drive is just one large partition. Find out how large 
it is _exactly_, and create a new partition on the new drive _exactly_ the 
same size. If there is any extra space left over ignore it. (In linux use 
cfdisk, also it has a mode to show the size of the drive in sectors.)

If you have enough space on the new drive for 2 partitions exactly the 
same size as the one on the bad drive do it, the extra one will be useful.

Now run the ddrescue command using the partition of the old one and the 
partition of the new one. Something like /dev/sda1 and /dev/sdb1 - but it 
will be different on your machine. Run cat /proc/partitions to get a list. 
Don't do it backward!

> 3.  Try to mount /dev/newdrive ???

You can try, but more likely you will want to boot windows and run 
chkdisk or scandisk.

Here is where the extra partition is useful. You copy the rescued data to 
the extra partition and try various tools (like checkdisk) on it to see 
which tool works best, but without disturbing your copy of the rescued 
data.

> 4.  If I it cannot be mounted, use PhotoRec to recover
> files ???

Don't know this tool.

Also, once ddrescue finishes I would run it again, but this time without 
the -n.

Also, I don't know how well or poorly it will work if run over USB - I 
don't know how USB reacts to errors. Presumably USB is slower then hooking 
it up direct. Every encountered error makes the computer try over and over 
to read it - very slow, perhaps USB doesn't try as often? Perhaps more 
often? You'll need to experiment, or find someone who has done it.

        -Ariel