[clug] Recovering data from old disks. Max age observed?

[Eyal Lebedinsky]

On 15/6/19 6:48 pm, steve jenkin wrote:
> Eyal,
> 
> No idea - ran ‘ddrescue’ with defaults.

The default is 3 passes.

I recently rescued a small HD, initially showing 3 bad sectors and after a few 100 pass runs.
This is what the last mapfile showed:

# Mapfile. Created by GNU ddrescue version 1.22
# Command line: ddrescue /dev/sda /home/partimag/ea-sda.dd /tmp/dd.map -d -r100 -vv
# Start time:   2019-05-21 03:34:38
# Current time: 2019-05-21 03:41:06
# Finished
# current_pos  current_status  current_pass
0x697A0F000     +               100
#      pos        size  status
0x00000000  0x697A0EE00  +
0x697A0EE00  0x00000200  -
0x697A0F000  0xC0A507000  +

The second last line shows one (0x200 bytes) bad (-) sector.

> no paramaters bar source & destination.
> 
> Those are really handy options it has - thanks very much,
> Next drive I try to recover, I’ll look at the options more closely.
> 
> I was impressed with only 17 errors.

Each pass attempts to rescue only the failed sectors, so very quick.
However, you should always use a mapfile (3rd positional arg) to allow doing more passes in followup runs.

I use something like:
	sudo ddrescue /dev/sdX rescue-sdX.dd rescue-sdX.map -d -r100 -vv
-d	use direct disc access for input file
-r100	exit after 100 retry passes
-vv	be very verbose, nice to see if bad sectors shrink

> Filesystem passed fsck and other checks, so not fussed with losses.

Good, bad sectors are often in unused sections of the fs (a mapfile shows where the bad sectors are).

cheers

> s
> 
>> On 15 Jun 2019, at 09:57, Eyal Lebedinsky via linux <linux at lists.samba.org <mailto:linux at lists.samba.org>> wrote:
>>
>> How many ddrescue passes did you use? I found that using a large number (say 500)
>> recovered many bad tracks for me when a disk goes funny.
>>
>> Of course, one may rarely get a false positive.
>>
>> cheers
>>
>> [trimmed]
>>
>> --
>> Eyal at Home (eyal at eyal.emu.id.au <mailto:eyal at eyal.emu.id.au>)
> 
> --
> Steve Jenkin, IT Systems and Design
> 0412 786 915 (+61 412 786 915)
> PO Box 38, Kippax ACT 2615, AUSTRALIA
> 
> mailto:sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

-- 
Eyal at Home (eyal at eyal.emu.id.au)