Re: [gentoo-user] Re: is ddrescue this slow?

[Valmor de Almeida]

On Sun, Jan 10, 2010 at 9:39 PM, Stroller
<stroller@××××××××××××××××××.uk> wrote:
>
[snip]
>
> I just reread the above ("from within systemrescuecd"), which implies you
> may be stuck without another working system.

Yes.
I am afraid the text below will be confusing but will send anyway.
Will be happy to send clarifications if needed. This is a resend (in
plain text) of another e-mail I sent with information on the LVM
partition on the broken drive.

>On Sat, Jan 9, 2010 at 11:10 AM, Stroller <stroller@××××××××××××××××××.uk> >wrote:
[snip]
>    I think Valmor is using GNU ddrescue, with which one makes the multiple >passes manually. The "-n" flag on the command line that Valmor posted >(`ddrescue -n /dev/sda /dev/sdc rescued.log`) relates to the examples given >in the GNU manual page [1]. I believe that GNU ddrescue is the better version >- it was inspired by garloff's original work, and makes improvements, but it >operates differently.


Indeed I am using GNU ddrescue and the -n flag is supposed to expedite
the recovery of data as posted in
http://www.cgsecurity.org/wiki/Damaged_Hard_Disk

"The best solution - both faster and more efficient - seems to be
Antonio Diaz's 'ddrescue' (ddrescue)"

# first, grab most of the error-free areas in a hurry:
./ddrescue -n /dev/old_disk /dev/new_disk rescued.log
# then try to recover as much of the dicy areas as possible:
./ddrescue -r 1 /dev/old_disk /dev/new_disk rescued.log


>    expectation, not a reasoned one. I think the best thing he can do is hold >his breath, wait until its finished and see how if the results are readable, after >running `fsck` on the mounted filesystem.


The first step above finished; don't know how long it took but it was
a long time (maybe 20 hours or more?) and the screen output was


Press Ctrl-C to interrupt
Initial status (read from logfile)
rescued:         0 B,  errsize:       0 B,  errors:       0
Current status
rescued:    58811 MB,  errsize:  48909 kB,  current rate:       83 B/s
   ipos:    58860 MB,   errors:      95,    average rate:    1365 kB/s
   opos:    58860 MB,     time from last successful read:       0 s
Copying non-tried blocks...
ddrescue: write error: Input/output error


Comparing with the screen output at the time of my first post,

Current status rescued went from 58656 MB to 58811 MB, errsize went
from 4408 kB to 48909 kB.

Don't know how the write error: Input/output error message affect the
data in the new drive copied to. Not sure whether I should do the next
step with option -r 1.

This failed drive is still bootable and the corruption is in the
partitions /var (which I do not care) and /home; these cannot be
mounted. I would like to attempt to get a couple of files from /home
that were not in the most recent backup. Maybe I should try to rescue
only the partition /home. However this partition is under LVM.
Specifically, /dev/sda4 is a linux LVM partition. The volume group is
vfda and the logical volume of interest is /dev/vfda/home which has
reiserfs file system. Is it possible to rescue data only from this
partition when under LVM?

>    Valmor: when I ran the `ddrescue -dr3` stage I had no success at all, >however the system was fine after a reboot & a `chkdsk`. Better than it had >been, in fact, on the old hard-drive. You might have more luck getting *some* >of the blocks showing as failed when you run it on your drive, but don't be >too disheartened if you don't.

>   Stroller.

Stroller, you mean your rescue.log showed no problematic entries? I
got over 400 lines in my rescue.log file.

root@sysresccd /root % head rescued.log
# Rescue Logfile. Created by GNU ddrescue version 1.11
# current_pos  current_status
0xDB45D9000     ?
#      pos        size  status
0x00000000  0x9CE341000  +
0x9CE341000  0x00000200  -
0x9CE341200  0x0001F000  *
0x9CE360200  0x00000200  -
0x9CE360400  0x00020000  *
0x9CE380400  0x3BD63AC00  +



Thanks for inputs.

--
Valmor