[plug] Help needed

Michael Van Delft michael at hybr.id.au
Mon Jul 16 11:02:54 WST 2012

This might be a few days late but there was a thread a while back "re;
bad block on disk" and it was said that ddrescue was much better on
failing disks than dd. /sbin/southen said
<snip  /sbin/southen>
dd is in my experience completely useless for recovery purposes, if
your distro lacks ddrescue grab SystemRescueCd.

As suggested, find a destination partition/drive (with twice the
needed space) and run:
 ddrescue -n /dev/sdb1 /mnt/recover/sdb1 /mnt/recover/sdb1.logfile
 ddrescue -d -r3 /mnt/recover/sdb1 /mnt/recover/sdb1.logfile
(where /dev/sdb1 is the partition or drive to rescue, and /mnt/recover
is a nice large partition)

The first pass tries to recover the most it can as fast as possible,
while the second tries to recover the parts that failed in the first
pass  in increasingly smaller chunks (by referring to the created
log). I have personally rescued all but a few hundred KB of 400GB
(over two ext4 partitions, ddrescue does whole drives too) that dd had
failed to copy beyond a couple of gig - if the drive gets kicked out
of /dev, unable to read at all, etc. you can restart the first pass
with -T to resume at full speed, while preserving what has been
successfully rescued (according to the log file).
Read the info pages for more details and examples.

I've also heard/seen people put the drive in the freezer and then wrap
it in a towel with ice packs to keep it cool while coping and it can
really make a difference.

If you haven’t got any other offers I’d be happy to give you a hand
with backing up your drive.

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