Re: I'd like to fix read failure issue on Mac OS X

Kimio Miyamura <[email protected]>
Newsgroups gmane.linux.utilities.smartmontools
Message-ID <[email protected]>
2014/12/17 18:49, Tim Small <tim <at> seoss.co.uk> wrote:

> If there's doubt about what the actual LBA is, then to be on the safe
> side, I would try and use dd to read the entire disk:
> 
> dd if=/dev/disk5 of=/dev/null bs=512
> 
> on Linux I'd also use iflag=direct to stop any OS level buffering, but
> don't know how this is done (if at all) on OSX.
> 
> You will then confirm where (if anywhere user-addressable) the error
> actually is.
> 
> Reconfirm using
> 
> dd if=/dev/disk5 of=/dev/null bs=512 skip=suspectedLBA count=1
> 
> (again adding option for direct I/O if possible).
> 
> 
> 
> I'd then use dd with bs=512 if=/dev/zero  count=1 seek=suspectedLBA to
> write to the correct disk device, and then confirm pending sector = 0 in
> smartctl output.

Sorry, I don't try this procedure yet...

> If you can't find the sector, then maybe the drive is using something
> like DCO.  In that case maybe best to use a Linux boot disk (something
> like GRML, which includes smartctl and hdparm) to proceed with minimal
> risk to your OS install.

I tried GRML live cd.  But may be something is wrong, I can't fix with hdparm or dd on live cd.
Here's fdisk result on live cd.

$ fdisk -ul /dev/sdb
                     Start           End                  Sectors           Size           Type
/dev/sdb1       40              409639            40960             200M        EFI
/dev/sdb2       409640      976510983      976101344      465.5G     Apple HFS/HFS+

So end sector of /dev/sdb2 976510983 < short test result 976783240...

I don't know why...


// Miya

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