how to fix "CORRUPT" partition table in mirrored drive

[Valeri Galtsev]

On Thu, June 25, 2015 7:04 pm, William Dudley wrote:
> Warren,
>
> Again, thanks for the reply.  Does the fact that gpart show -l reports
> this:
>
> =>        63  3907029104  mirror/gm0  MBR  (1.8T) [CORRUPT]
>
> Mean that I'm screwed and must copy all the data to a new drive and
> create the mirror anew?
>
> Can I remove the second drive from the mirror and still have the data on
> it
> accessible?
> the gmirror man page doesn't say what the disks that are removed from the
> mirror "look like",
> i.e. are they in some wierd format or can they be read like a normal disk.
>
> Thanks,
> Bill Dudley
>
>
> This email is free of malware because I run Linux.

I wouldn't say that this statement is strictly speaking correct.

Valeri

>
> On Thu, Jun 25, 2015 at 7:57 PM, Warren Block <wblock at wonkity.com> wrote:
>
>> On Thu, 25 Jun 2015, William Dudley wrote:
>>
>>  I have a mirrored drive:
>>>
>>> gpart show -l
>>> =>      63  78156225  ad0  MBR  (37G)
>>>        63  78156162    1  (null)  [active]  (37G)
>>>  78156225        63       - free -  (31k)
>>>
>>> =>       0  78156162  ad0s1  BSD  (37G)
>>>         0  41943040      1  (null)  (20G)
>>>  41943040   2097152      2  (null)  (1.0G)
>>>  44040192  34115970      4  (null)  (16G)
>>>
>>> =>        63  3907029104  mirror/gm0  MBR  (1.8T) [CORRUPT]
>>>          63  3907029105           1  (null)  [active]  (1.8T)
>>>
>>> =>         0  3907029105  mirror/gm0s1  BSD  (1.8T)
>>>           0   335544320             4  (null)  (160G)
>>>   335544320   209715200             5  (null)  (100G)
>>>   545259520   209715200             6  (null)  (100G)
>>>   754974720  3152054385             7  (null)  (1.5T)
>>>
>>> I tried to fix the corrupt partition table like this:
>>>
>>> gpart recover mirror/gm0
>>> gpart: recovering 'mirror/gm0' failed: Function not implemented
>>>
>>> So how do I fix the corrupt partition table?  Can I un-mirror the two
>>> drives
>>> and then do the gpart recover and then re-mirror them?
>>>
>>
>> gpart recover only works with some partitioning schemes.  GPT has a
>> backup
>> copy of the partition table that can be used to recover the primary one.
>> MBR and BSD partitioning schemes do not have redundant metadata for
>> recover
>> to use.
>>
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++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++