[RndTbl] Open Source Backup/cloning to USB HDD

[Daryl F]

To (sometimes) get around dd stopping on the first error or using 'noerr' 
and getting nothing copied for a sector, I've been using a program called 
ddrescue ref: http://directory.fsf.org/project/ddrescue/ that does several 
retries before giving up. It also has some interesting techniques to 
recover as much as possible from a damaged disks while minimizing further 
damage.

-Daryl


On Tue, 27 Oct 2009, Dan Martin wrote:

> I have used dd for copying drives or partitions in the past, in order to
> have a clone ready to swap in in the event of a failure.  I found it
> extremely useful, much faster than some cheap commercial software.
>
> One problem I have encountered is IO errors, especially when copying large
> volumes.  The 'noerr' option allows the copy to complete, but of course does
> not correct the problem.  I have had one or two errors on every second
> drive.
>
> For my Mac, I have some commercial software that can find the error and what
> file (if any) it affects.  It can report the error to the HSF+ file system,
> so that no other files use that sector.
>
> I can't find any material that explains how this works -- what I surmise is
> that the drive firmware hides defective blocks.  Obviously it does not hide
> them all, or at least not instantly - so the file system tracks bad blocks
> that the firmware has missed in order to avoid using them in files.  Using
> dd circumvents the file system, so there is a risk of a corrupt file on the
> target drive/partition.
>
> The drives seem OK in every other respect, and software that monitors the
> status of the drives does not indicate any impending failure.  I am
> guessing, based on a small sample, that this is a 'normal' condition.
>
> On Tue, Oct 27, 2009 at 3:36 PM, John Lange <john at johnlange.ca> wrote:
>
>> Just out of curiosity, what is it that these various programs that
>> people have recommended do with regard to imaging that "dd" doesn't?
>>
>> I've never looked at any of these in any great detail but so far as I
>> can see they all add complexity while reducing functionality.
>>
>> Image a disk? dd
>>
>> Backup a file system? rsync
>>
>> to tape? tar
>>
>> to remote? ssh (or scp)
>>
>> scheduled? put any of the above in cron
>>
>> That's all you need. What am I missing?
>>
>> Regards,
>> --
>> John Lange
>> http://www.johnlange.ca
>>
>> On Tue, 2009-10-27 at 15:26 -0500, Montana Quiring wrote:
>>> This is from Clonezilla page:
>>> Based on Partimage, ntfsclone, partclone, and dd to clone partition.
>>> However, clonezilla, containing some other programs, can save and
>>> restore not only partitions, but also a whole disk.
>>>
>>> Thanks for the feedback everyone!
>>
>>
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>
>
>
>

-Daryl