Date: Thu, 23 Mar 2017 15:59:03 -0400
To: Stephen Mueller <stephen@mueller.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: RAID array is gone, please help
Message-ID: <20170323195903.GO14186@csclub.uwaterloo.ca>
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From: lsorense@csclub.uwaterloo.ca (Lennart Sorensen)
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On Thu, Mar 23, 2017 at 08:38:08PM +0100, Stephen Mueller wrote:
> Apologies, I should have started this on linux-raid...
> 
> 
> stephen@fred> sudo gdisk -l /dev/sdc
> GPT fdisk (gdisk) version 1.0.1
> 
> Partition table scan:
>   MBR: protective
>   BSD: not present
>   APM: not present
>   GPT: present
> 
> Found valid GPT with protective MBR; using GPT.
> Disk /dev/sdc: 7814037168 sectors, 3.6 TiB
> Logical sector size: 512 bytes
> Disk identifier (GUID): 60F1D54C-9D17-4688-BD6E-447F5E7408EB
> Partition table holds up to 128 entries
> First usable sector is 34, last usable sector is 7814037134
> Partitions will be aligned on 2048-sector boundaries
> Total free space is 7814037101 sectors (3.6 TiB)
> 
> Number  Start (sector)    End (sector)  Size       Code  Name
> stephen@fred>
> 
> The other disks are all similar.
> 
> How do I remove the MBR/GPT tables? So you would do that, and then the
> mdadm --create?

Well at least that seems to confirm that something restored the GPT from
the second copy at the end of the disk, wiping out the md superblock
at 4k.

If you run gdisk /dev/sdc, it has a 'zap' option using the z key to
delete all traces of GPT.  That ought to do what you want.

-- 
Len Sorensen