[TriLUG] OT: Laptop Hard Drive
ncdave4life at gmail.com
Sat Nov 19 09:22:16 EST 2011
On Sat, Nov 19, 2011 at 8:25 AM, Joseph Mack NA3T <jmack at wm7d.net> wrote:
> On Fri, 18 Nov 2011, David Burton wrote:
> ddrescue will never recover part of a sector. SpinRite will do that, but
>> ddrescue either recovers a sector or it doesn't, nothing in-between.
> if sector 0,1 and 3 are OK, but sector 2 is not, what does ddrescue do on
> the target piece of disk? write 0,1, then hop over 2 leaving whatever junk
> was there and then write 3?
Note, however, that the ddrescue "log file" keeps track of which sectors
have been recovered and which have not. I.e., you can tell the difference
between the recovered data and "whatever junk was there."
In recent versions of ddrescue there is also a "--fill" option that can be
used to write zeros to unrecovered sectors; see "fill mode" in the
(A variant of the --fill option does the opposite: aim it at the bad drive,
and it writes zeros everywhere except the bad sectors, so that you can
return the drive for warranty replacement and it will still test bad, but
will not contain any of your data.)
Also, some versions of Linux (including Parted Magic) apparently don't let
ddrescue access individual sectors, even with the the -d option specified.
On those versions of Linux, the granularity is usually 4kb (8 sectors), so
if any of the 8 sectors in a cluster are unreadable the other 7 are
unrecovered, as well.
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