CentOS - Sep 2020 - Using CentOS 7 to attempt recovery of failed disk

I have a disk that is flagging errors, attempting to rescue the data.

I tried dd first - if gets about 117G of 320G disk and stops incrementing
the save image any more.

Now I'm trying ddrescue and it also stops about the same point

Thoughts on how to continue past that point ?
Thanks,

Jerry

> On Sep 26, 2020, at 8:05 AM, Jerry Geis <jerry.geis at gmail.com>
wrote:
> 
> I have a disk that is flagging errors, attempting to rescue the data.
> 
> I tried dd first - if gets about 117G of 320G disk and stops incrementing
> the save image any more.
did you try

dd conv=noerror ?

this flag makes dd not stop on input error. Whatever is irrecoverable is
irrecoverable, but this way you will get stuff beyond failure point.

Valeri
> 
> Now I'm trying ddrescue and it also stops about the same point
> 
> Thoughts on how to continue past that point ?
> Thanks,
> 
> Jerry
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> https://lists.centos.org/mailman/listinfo/centos

Also, does ddrescue "stop" (as in quit) or is it just stuck there
spending
a lot of time trying to read one or more bad spots? it is intended to keep
trying until it gets something, or gives up and skips to the next
track/sector/whatever. If you let it go for a long time (overnight???) does
it proceed ?

On Sat, Sep 26, 2020 at 9:15 AM Valeri Galtsev <galtsev at
kicp.uchicago.edu>
wrote:
>
>
> > On Sep 26, 2020, at 8:05 AM, Jerry Geis <jerry.geis at
gmail.com> wrote:
> >
> > I have a disk that is flagging errors, attempting to rescue the data.
> >
> > I tried dd first - if gets about 117G of 320G disk and stops
incrementing
> > the save image any more.
>
> did you try
>
> dd conv=noerror ?
>
> this flag makes dd not stop on input error. Whatever is irrecoverable is
> irrecoverable, but this way you will get stuff beyond failure point.
>
> Valeri
>
> >
> > Now I'm trying ddrescue and it also stops about the same point
> >
> > Thoughts on how to continue past that point ?
> > Thanks,
> >
> > Jerry
> > _______________________________________________
> > CentOS mailing list
> > CentOS at centos.org
> > https://lists.centos.org/mailman/listinfo/centos
>
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> https://lists.centos.org/mailman/listinfo/centos
>

Hello

I did try the "dd conv=noerror ?"
The ddrescue - doesnt stop - it just doesnt "continue" past a certain
point. Somewhere around the 117G mark - it just doesnt go past that .
(same with dd, gets to 117G and just doesnt continue.
I have let the dd run all night - did not go past the 117G.

Thanks for any suggestions.

Jerry

Well, I'm not a noted expert on ddrescue, but my limited experience tells
me that when it hits bad spots (or a big cluster of them) it can go very
slowly as it tries multiple times to read each sector (or track, I'm not
sure which, in this case). It keeps a list of bad spots and goes back at
the end to try again to read something from them. Of course, if you've had,
eg. a head crash, there's probably nothing there to read.

On Sat, Sep 26, 2020 at 1:41 PM Jerry Geis <jerry.geis at gmail.com>
wrote:
> Hello
>
> I did try the "dd conv=noerror ?"
> The ddrescue - doesnt stop - it just doesnt "continue" past a
certain
> point. Somewhere around the 117G mark - it just doesnt go past that .
> (same with dd, gets to 117G and just doesnt continue.
> I have let the dd run all night - did not go past the 117G.
>
> Thanks for any suggestions.
>
> Jerry
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> https://lists.centos.org/mailman/listinfo/centos
>

On 9/26/20 12:40 PM, Jerry Geis wrote:
> Hello
> 
> I did try the "dd conv=noerror ?"
> The ddrescue - doesnt stop - it just doesnt "continue" past a
certain
> point. Somewhere around the 117G mark - it just doesnt go past that .
> (same with dd, gets to 117G and just doesnt continue.
> I have let the dd run all night - did not go past the 117G.
You can interrupt ddrescue and then resume with "-R" (--reverse)
option. That will make it start from the end of the device and read backward
toward the trouble area.

-- 
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.

In article <E02FA554-9D6D-4E7D-8A78-5FBDE1DE939D at kicp.uchicago.edu>,
Valeri Galtsev <galtsev at kicp.uchicago.edu>
wrote:
> 
> 
> > On Sep 26, 2020, at 8:05 AM, Jerry Geis <jerry.geis at
gmail.com> wrote:
> > 
> > I have a disk that is flagging errors, attempting to rescue the data.
> > 
> > I tried dd first - if gets about 117G of 320G disk and stops
incrementing
> > the save image any more.
> 
> did you try
> 
> dd conv=noerror ???
> 
> this flag makes dd not stop on input error. Whatever is irrecoverable is
irrecoverable, but this way you will get stuff
> beyond failure point.
You need conv=noerror,sync so that unreadable sectors get replaced by zeros
instead of not being written out at all.
Without sync, the filesystem geometry on the destination image will be wrong
after the first error.

You also need bs=4096 so that ONLY the bad sector(s) get zeroed, and not the
surrounding ones. If you have, say,
bs=1M, then you will get a megabyte of zeros if any block within that megabyte
is bad.

I'm speaking from recent experience!

Cheers
Tony

-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org

Thanks everyone for the suggestions. I finally got a completion with this
command:

dd conv=noerror,sync iflag=direct bs=4096 if=/dev/sdb of=disk.img

Copying it now to see if it worked.

Jerry