SUMMARY: Metadisk and data retrieval

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To: sunmanagers@sunmanagers.org
Date: 02 Dec 2003 15:42:49 +1030

Original question follows.

Lots of out of office replies.

The following solution from Eugene and John did allow me to mount the
metadevice. There were problems with listing permissions and not
everything was accessible. In my case it was not good enough to be worth
retrieving the data and it was un-fsckable to get it into any better
shape.

Thanks John & Eugene

           From:
Eugene Schmidt
<fereug@acute.co.za>
             To:
Martin de Koning
<martindk@trinity.sa.edu.au>
        Subject:
RE: Metadisk and
data retrieval
           Date:
Mon, 1 Dec 2003
09:49:02 +0200

Hi

My guess is that you "could" do. I would do something like the
following:

metaclear d0

metainit d0 2 1 c0t1d0s5 \
         1 c0t2d0s5

mount -o ro /dev/md/dsk/d0 /export/home

You should be able to see the first lot of data, however be prepared for
errors.

Another factor would be how full the disk was. If all 3 were of equal
size
and you used more than 66% of the total size, we would be using the 3rd
disk. However, even so, if I was writing a large file, that would
fragment
on the first two, it woul write to the 3rd. This file could also be an
updated version of a previous that has grown.

Do not try while people are on the system, you could get a panic or two.

Regards

Eugene

                             From:
John Furlong
<jfurlong@dsl.pipex.com>
                               To:
Martin de Koning
<martindk@trinity.sa.edu.au>
                          Subject:
Re: Metadisk and data retrieval
                             Date:
Mon, 01 Dec 2003 09:44:33 +0000

Hello Martin,

What you want MAY be possible, no guarantees. The problem will be with
the
file system, not the metadevice. The file system will be smaller than is
should be so fsck will always fail, but if the file system is clean you
will
be able to mount it and get your data off.

Here's what you do....

    metaclear d0
    metainit d0 2 1 c0t1d0s5 1 c0t2d0s5

That will get you a smaller d0 back, but as I say any problems will be
at
the file system level.

Hope this helps,

John.

On Mon, 2003-12-01 at 16:47, Martin de Koning wrote:
> Hi,
>
> I have a Sun E450 server with Solaris 8 originally set up by someone
> else with a metadisk for /export/home
>
> Contents of /etc/lvm/md.cf:
>
> # metadevice configuration file
> # do not hand edit
> d0 3 1 c0t1d0s5 \
> 1 c0t2d0s5 \
> 1 c0t3d0s5
>
> Now the c0t3d0 disk has failed, rendering the metadisk unusuable. But
> since it consists of 3 concatenated disks and the data stored on is less
> then a 3rd of the available space, I was wondering if it is possible to
> reconstruct the data from the two remaining disks?
>
> If not I will create a device consisting of the two remaining disks
> mirrored.
>
> Cheers
> Martin

-- 
Martin de Koning <martindk@trinity.sa.edu.au>
Trinity College Gawler Inc.
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