Re: [Bug-ddrescue] Handling drives that have broken partition table?

[Narcis Garcia]

How do you know what is happening between these 2 possibilities:

A) The drive is in "device fault" ever.
B) The drive goes into "device fault" at first Linux read error.

In both cases when the user tries to read data, should find same "device
fault" situation.


On 07/02/16 12:48, Robert Backhaus wrote:
> So, the fault here is twofold - 1. a drive with faulty firmware that
> disables itself when a read is made, and 2. the apparent lack of a
> method to prevent linux from doing a partition table scan on device
> attachment.
> 
> Neither of these can be addressed by developers of ddrescue. However, If
> you or anyone else finds, or can get someone to implement, a method to
> prevent linux from reading partition tables, or ways to resurrect
> firmware locked drives, we will be all ears.
> 
> On 7 February 2016 at 19:53, Narcis Garcia <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     You are asking for a low level cache (editable cache), and it could be
>     much interesting for sector 0 problems and other situations.
> 
>     I don't know if deploying a RAID1 simulation could make Linux to read
>     bad sectors from mirror device.
> 
> 
> 
>     On 07/02/16 04:15, Paul Daniels wrote:
>     > Sorry, I should have been more specific about the particular situation
>     > that arises.
>     >
>     > When sector-0/partition-table is physically damaged and non-recoverable
>     > it sometimes causes the drive to "offline" itself when you try to read
>     > it, as such you can never recover these drives with ddrescue+linux
>     > because linux will attempt to read that partition table each time you
>     > power the drive up.
>     >
>     > What would be nice is if there was an overlay facility/magic in linux
>     > where, if you already had a copy of the data in that area (or even just
>     > fake), you could make linux read the partition/data from the image/clone
>     > and switch to the real drive for other areas.
>     >
>     > Hope that clears matters up.
>     >
>     >
>     > On 07/02/16 03:09, Narcis Garcia wrote:
>     >> Partition table and drive presence are 2 unrelated things.
>     >> Partition table is data, and drive is a device.
>     >> Sector 0 should be copiable without any MBR/GPT/etc data in it.
>     >>
>     >>
>     >> On 06/02/16 14:08, Cameron Andrews wrote:
>     >>> That doesn't work though if Linux says "nope, there is no drive
>     here"
>     >>> when it cannot find the partition table..  ie: the /dev/sdX is not
>     >>> present for the drive because no table was readable...
>     >>>
>     >>> On 06/02/16 03:31, Antonio Diaz Diaz wrote:
>     >>>> Narcis Garcia wrote:
>     >>>>> Number of disk sectors could be specified to ddrescue?
>     >>>> Sure:
>     >>>>    ddrescue --size=123456s
>     >>>>
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