Idle though on ddrescue and clonezilla

[David]

Running the data recovery at the moment on my dodgy Seagate 3TB drive,
using ddrescue-gui.

I took a conservative route of creating new partitions on the new drive to
rescue to, but glancing through the options it looks as though you can
just clone a complete drive.

So is ddrescue a sensible alternative to clonezilla?

Clones a drive with the additional feature that it can recover from
corruptions?

I assume it will be slower (but by how much?) but safer.

Just an idle thought without doing anything close to a feature-by-feature
comparison.

Cheers


Dave R


--
Windows 8.1 on PCSpecialist box

[Johnny B Good]

On Wed, 29 Jun 2016 13:33:57 +0000, David wrote:

> Running the data recovery at the moment on my dodgy Seagate 3TB drive,
> using ddrescue-gui.
>
> I took a conservative route of creating new partitions on the new drive
> to rescue to, but glancing through the options it looks as though you
> can just clone a complete drive.
>
> So is ddrescue a sensible alternative to clonezilla?

In the case of a dodgy or failing drive, well, Hell Yes!!!

>
> Clones a drive with the additional feature that it can recover from
> corruptions?

Presumably you're referring to the show stopping effect of seriously
corrupted sectors which cause the controller in the failing drive to
throw its hand in and refuse any further co-operation with ordinary
cloning software.

ddrescue knows just how to handle this situation. It logs the fact and
forces a reset of the drive's controller and retries to confirm which
range of sectors are poisonous to the drive's controller so it can skip
around them.

>
> I assume it will be slower (but by how much?) but safer.

If anything (when cloning a failing drive at least), it will actually be
faster (and safer as a result) since it can prioritise its data recovery
to those sectors that remain easily readable, leaving the bad areas to
last rather than mindlessly persisting in dealing with impossible to
recover sectors, delaying the whole process by days, if not weeks, by
which time the rest of the still readable sectors may well have suffered
further corruption or the controller finally gives up the ghost
altogether.

>
> Just an idle thought without doing anything close to a
> feature-by-feature comparison.
>

There's no need for such a comparison. If you had read the ddrescue info
file or the on line documentation, you'd *know* that ddrescue is
incomparably superior to any other cloning tools when it comes to data
recovery from "Dodgy" or failing drives.

--
Johnny B Good

[Gordon]

While ddrescue may clone disks the key part is rescue. Cloning the disk is
really nothing more than a by product of data rescue. Data rescue is what
one is trying to do with ddrescue in the first instance, not clone the disk.

Clonezilla, clones disk and she is some what fussy. Throws up an error
message and stops if she can not read the disk.

[Jaimie Vandenbergh]

Johnny B Good <johnny...@invalid.ntlworld.com> wrote:
>

> There's no need for such a comparison. If you had read the ddrescue info
> file or the on line documentation, you'd *know* that ddrescue is
> incomparably superior to any other cloning tools when it comes to data
> recovery from "Dodgy" or failing drives.

It's a terrible general purpose cloning tool though, not recommended for
that at all. It has no interest in anything above the block layer, so no
features for resizing partitions, alignment, or modifying structures to fit
on a slightly different size disk.

It's good for bad-sector disk rescue, identical disk-to-disk cloning, and
basically nothing else.

Cheers - Jaimie

[David]

I think I may not have stated my premise clearly enough :-)

Since ddrescue is infinitely superior to clonezilla when rescuing a dodgy
drive, is there any reason not to use it when cloning a perfectly working
drive?

It should just do the cloning and not find any errors.

So is clonezilla faster with more features, or is ddrescue also the
software of choice for cloning healthy drives?

[David]

Thanks - we posted at about the same time so you answered my original
question as I was re-stating it.

[Johnny B Good]

It's not quite so bad as Jamie painted it. You can use ddrescue to
create images of individual partitions (although I've yet to use it that
way) and there is certainly no problem cloning to a larger drive where
you can resize the partition after running any FS repair operations
afterwards.

Ordinary cloning tools which understand the file systems in use can
avoid cloning free sectors and instantly create empty 'content free'
files such as page, hibernate or swap files, which can speed up the
process considerably, especially on large disk volumes with large amounts
of free space. However, they rely on the source disk being free of bad
sectors or any other issues as a result of impending failure. Any such
problems will slow or even stop these cloning / imaging tools dead in
their tracks.

When you're trying to clone a "Problem Disk", using ddrescue is a "No
Brainer". If you're cloning a disk that's even just slightly suspect, it
makes sense to forego the 'intelligent' cloning option and use ddrescue
instead. After all, "Better late than never!" is a key description of a
successful data recovery operation. :-)

--
Johnny B Good

[Johnny B Good]

On Thu, 30 Jun 2016 09:43:51 +0000, David wrote:

> On Thu, 30 Jun 2016 05:52:37 +0000, Gordon wrote:
>
>> On 2016-06-29, Johnny B Good <johnny...@invalid.ntlworld.com>
>> wrote:
>>> On Wed, 29 Jun 2016 13:33:57 +0000, David wrote:
>>>
>>>
>>>> Just an idle thought without doing anything close to a
>>>> feature-by-feature comparison.
>>>>
>>>>
>>> There's no need for such a comparison. If you had read the ddrescue
>>> info
>>> file or the on line documentation, you'd *know* that ddrescue is
>>> incomparably superior to any other cloning tools when it comes to data
>>> recovery from "Dodgy" or failing drives.
>>>
>>>
>> While ddrescue may clone disks the key part is rescue. Cloning the disk
>> is really nothing more than a by product of data rescue. Data rescue is
>> what one is trying to do with ddrescue in the first instance, not clone
>> the disk.
>>
>> Clonezilla, clones disk and she is some what fussy. Throws up an error
>> message and stops if she can not read the disk.
>
> I think I may not have stated my premise clearly enough :-)
>
> Since ddrescue is infinitely superior to clonezilla when rescuing a
> dodgy drive, is there any reason not to use it when cloning a perfectly
> working drive?

If you're confident about the state of health of the source drive, then
it's a matter of time constraints. ddrescue will take longer than a File
System aware 'intelligent' cloning tool which can not only skip cloning
free space but usually know how to instantly create content free files
such as page, hibernate or swap files on the target disk volume. Also
cloning large capacity disk volumes with a large percentage of free space
will be considerably faster to clone than using ddrescue.

ddrescue can get the job done regardless of whether the drive is failing
or not. In the case of a perfectly good drive, it may not be the best
option to go for. I've used ddrescue to clone what I've assumed to be
perfectly good disk drives but these were disk drives with very little
free space and little to no 'content free' files to needlessly bog down
the process.

>
> It should just do the cloning and not find any errors.
>
> So is clonezilla faster with more features, or is ddrescue also the
> software of choice for cloning healthy drives?

Clonezilla would be first choice when cloning healthy disk drives and
ddrescue first choice when cloning or imaging failing drives. The only
time when you might want to use ddrescue to clone a healthy drive is when
the likes of Clonezilla cannot recognise the file system in use. In this
eventuality, you can choose the dumb sector by sector option normally
available in all intelligent cloning tools.

However, if Clonzilla is reduced to this method, you may as well use
ddrescue to clone the disk (it won't be any slower and should any
unexpected problems with bad sectors arise, you won't be faced with a
show stopping situation short of a sudden and total catastrophic disk
failure). Even when ddrescue is brought to a halt by such catastrophic
failure, you may still be able to recover vital data from the partially
cloned disk or image file.

Both utilities will get the job done with healthy disk drives but
clonezilla is a better fit when dealing with known file systems since it
can not only keep the job time to a minimum, it also minimises the wear
and tear on the drives.

--
Johnny B Good