[ale] possible to use hard drives that have bad blocks ?

[Greg Freemyer]

On 6/25/05, Courtney Thomas <ccthomas at joimail.com> wrote:
> I've got a couple of HDs that when I:
> 
> dd if=/dev/hdX of=/dev/null bs=1m
> 
> I get a single instance of something like:
> 
> FAILURE - READ_DMA status=51 <READY, DSC, ERROR> error=40
> <UNCORRECTABLE> LBA=19194112 Input/output error
> 
> My question is: does this signify a single bad block and is there a way
> to identify this error to some program that can block it's use, so the
> drive can be used ?
> 
> Thank you,
> Courtney
> 

LBA is the Logical Block Address of the physical sector on the drive.

If indeed your only seeing one LBA address that is consistently bad
you should be able fix it.

If your a C programmer, you could open /dev/hdX, lseek to LBA * 512
and try to read a sector (512) bytes.  It should cause the same error.
 If not, try (LBA - 1) * 512.

If you can find the sector, then modify your code to write to the
sector.  That should either refresh the sector with a stronger
magnetic field, or cause an internal disk problem that causes the disk
to reassign the sector internally.

I would try the above before I started looking at filesystem level solutions.

Unfortunately, I don't know of a standard Linux tool to do the above,
but I'm sure there is one.  (dd with the skip option is very slow
because it actually reads everything being skipped).

Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century