Re: mdXX: bitmap superblock UUID mismatch

["Mathias Burén" <mathias.buren@gmail.com>]

On 14 February 2011 16:33, Reynald Borer <reynald.borer@gmail.com> wrote:
> Hi,
>
> Nice catch for the 1 bit difference, I didn't see it. My point
> regarding bitmap reconstruction was because this raid was used in a
> LVM setup. the LVM partition used two distinct raid 1 disks, and I was
> not able to start the LVM correctly without this failing raid.
>
> In the end, I was able to save my LVM by simply skipping the raid 1
> and using directly one partition. The LVM tool was clever enough to
> detect the MD bits and proposed me to remove them in order to mount
> directly the partition, and it worked fine. Thus I was able to save my
> data.
>
> Thanks for your answer though.
>
> Regards,
> Reynald
>
>
> On Thu, Jan 27, 2011 at 9:53 PM, NeilBrown <neilb@suse.de> wrote:
>> On Wed, 26 Jan 2011 21:58:25 +0100 Reynald Borer <reynald.borer@gmail.com>
>> wrote:
>>
>>> Hello guys,
>>>
>>> I have been using md raids for quite a long time now and it always
>>> worked fine, until recently when I upgraded some hardware on my
>>> workstation. Unfortunately the hardware I changed proved itself to be
>>> very unstable, and I encountered a lot of hard lockups of the system
>>> while running. Those lockups recently made one of my raid 1 array
>>> fails with the infamous error message "mdXX: bitmap superblock UUID
>>> mismatch".
>>>
>>> Here is what I have found in the kernel logs when I try to activate
>>> the given raid group:
>>> -----------------
>>> md/raid1:md126: active with 2 out of 2 mirrors
>>> md126: bitmap superblock UUID mismatch
>>> md126: bitmap file superblock:
>>>          magic: 6d746962
>>>        version: 4
>>>           uuid: 37102258.af9c1930.b8397fb8.eba356af
>>                           ^ this is an 'a'
>>
>>>         events: 199168
>>> events cleared: 199166
>>>          state: 00000000
>>>      chunksize: 524288 B
>>>   daemon sleep: 5s
>>>      sync size: 248075584 KB
>>> max write behind: 0
>>> md126: failed to create bitmap (-22)
>>> -----------------
>>>
>>>
>>> Such error messages are displayed each time I try to run the raid
>>> group. Content of /proc/mdstat is:
>>> -----------------
>>> md126 : inactive sdb6[0] sda6[1]
>>>       496151168 blocks
>>> -----------------
>>>
>>>
>>> If I try to examine both disks with mdadm -E it shows some checksum
>>> mismatch for both partitions:
>>> -----------------
>>> root@bob # mdadm -E /dev/sda6
>>> /dev/sda6:
>>>           Magic : a92b4efc
>>>         Version : 0.90.03
>>>            UUID : 37102258:bf9c1930:b8397fb8:eba356af
>>                             ^ this is a 'b'
>>
>> So you certainly do have some sick hardware!!!
>>
>> I suggest that you find some hardware that you can trust,
>> mount one of the two devices ( (sdb6 or sda6) ignoring the raid stuff,
>> and copy data off to the device that you trust.
>>
>> Then start again.
>>
>> NeilBrown
>>
>>
>>>   Creation Time : Mon Aug  7 21:06:47 2006
>>>      Raid Level : raid1
>>>   Used Dev Size : 248075584 (236.58 GiB 254.03 GB)
>>>      Array Size : 248075584 (236.58 GiB 254.03 GB)
>>>    Raid Devices : 2
>>>   Total Devices : 2
>>> Preferred Minor : 6
>>>
>>>     Update Time : Wed Jan 12 00:12:44 2011
>>>           State : clean
>>>  Active Devices : 2
>>> Working Devices : 2
>>>  Failed Devices : 0
>>>   Spare Devices : 0
>>>        Checksum : e4883f8e - expected e4883e8e
>>>          Events : 199168
>>>
>>>
>>>       Number   Major   Minor   RaidDevice State
>>> this     1       8       38        1      active sync
>>>
>>>    0     0       8       70        0      active sync
>>>    1     1       8       38        1      active sync
>>> root@bob # mdadm -E /dev/sdb6
>>> /dev/sdb6:
>>>           Magic : a92b4efc
>>>         Version : 0.90.03
>>>            UUID : 37102258:bf9c1930:b8397fb8:eba356af
>>>   Creation Time : Mon Aug  7 21:06:47 2006
>>>      Raid Level : raid1
>>>   Used Dev Size : 248075584 (236.58 GiB 254.03 GB)
>>>      Array Size : 248075584 (236.58 GiB 254.03 GB)
>>>    Raid Devices : 2
>>>   Total Devices : 2
>>> Preferred Minor : 6
>>>
>>>     Update Time : Wed Jan 12 00:12:44 2011
>>>           State : clean
>>>  Active Devices : 2
>>> Working Devices : 2
>>>  Failed Devices : 0
>>>   Spare Devices : 0
>>>        Checksum : e4883fac - expected e4883eac
>>>          Events : 199168
>>>
>>>
>>>       Number   Major   Minor   RaidDevice State
>>> this     0       8       70        0      active sync
>>>
>>>    0     0       8       70        0      active sync
>>>    1     1       8       38        1      active sync
>>> -----------------
>>>
>>>
>>> Any idea how I could try to save my raid group?
>>>
>>> Thanks in advance for your help.
>>>
>>> Best Regards,
>>> Reynald
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Wow, that's cool. I suppose RAID1 is simple enough for this to be
possible, though. Still, cool. :-)

// M
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html