linux-kernel - Re: RAID array is gone, please help

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Message-ID: <a135b9a4-ab7f-c368-fc1a-db53f46ea631@mueller.org>
Date:   Thu, 23 Mar 2017 21:09:39 +0100
From:   Stephen Mueller <stephen@...ller.org>
To:     Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: RAID array is gone, please help

OK, I used gdisk to remove the GPT and MBR from each disk.
mdadm --assemble still doesn't work... says it can't find the
superblock. The mdadm --examine commands also say that no
superblock is detected.

I guess I'll go ahead with --create...


On 3/23/2017 20:59, Lennart Sorensen wrote:
> On Thu, Mar 23, 2017 at 08:38:08PM +0100, Stephen Mueller wrote:
>> Apologies, I should have started this on linux-raid...
>>
>>
>> stephen@...d> 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@...d>
>>
>> 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.
>