Reassemble Raid 6

Reassemble Raid 6

[Justin Stephenson]

Hello,

I have reviewed the Linux Raid Wiki regarding rebuilding and it 
recommended writing a note to the list.

I am running an mdadm raid on CENTOS 6.5 with 6 disks in a Raid 6 off of 
my motherboard's SATA controller.

I added a 7th disk as a spare.

When I rebooted the raid after adding the spare, it would not mount and 
the OS would only boot into recovery mode. I changed my fsck file to 
exclude the raid and can now boot into the GUI.

I have tried to reassemble the array using --assemble and I get the the 
following message:

mdadm: we match both /dev/md/BigBlue:0 and /dev/md0 - cannot decide 
which to use.

I am including the output of the mdadm --examine below.

I am considering using --force to assemble the array, though I suspect 
that this is something simple that I am overlooking -- I am quite new to 
linux.

Any input would be appreciated.

- Justin

/dev/sdb1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : 7f7ace48:01a4b6f6:bf182ae3:6acddef9

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : cedf7f63 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : spare
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sdc1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : 8a4d11bd:fe387740:1edc1151:b0ebba43

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : 44a6c909 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 0
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sdd1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : aa158e32:f4449a9b:73e95000:22852278

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : f8ed43e6 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 1
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sde1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : 7bee5d42:cb66c602:162e88f1:e140447c

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : 65423ef2 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 2
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sdf1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : b4a7b35c:6e377711:4b291874:edb2c4d0

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : 65593610 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 3
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sdg1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : 7c0bba5a:6b205302:d026a78d:91f5ebdd

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : 7af1c2ff - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 4
    Array State : AAAAAA ('A' == active, '.' == missing)
/dev/sdh1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 0849c677:64e4772e:8892d80b:47e0097a
            Name : BigBlue:0  (local to host BigBlue)
   Creation Time : Wed Jan 15 22:46:32 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5860267024 (2794.39 GiB 3000.46 GB)
      Array Size : 11720533504 (11177.57 GiB 12001.83 GB)
   Used Dev Size : 5860266752 (2794.39 GiB 3000.46 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : a750a146:7ee7383e:2929d803:2bee9dc1

     Update Time : Sun Feb  9 20:31:13 2014
        Checksum : fca1ca30 - correct
          Events : 557

          Layout : left-symmetric
      Chunk Size : 128K

    Device Role : Active device 5
    Array State : AAAAAA ('A' == active, '.' == missing)

Re: Reassemble Raid 6

[Phil Turmel]

On 02/10/2014 11:48 AM, Justin Stephenson wrote:
> Hello,
> 
> I have reviewed the Linux Raid Wiki regarding rebuilding and it
> recommended writing a note to the list.
> 
> I am running an mdadm raid on CENTOS 6.5 with 6 disks in a Raid 6 off of
> my motherboard's SATA controller.
> 
> I added a 7th disk as a spare.
> 
> When I rebooted the raid after adding the spare, it would not mount and
> the OS would only boot into recovery mode. I changed my fsck file to
> exclude the raid and can now boot into the GUI.
> 
> I have tried to reassemble the array using --assemble and I get the the
> following message:
> 
> mdadm: we match both /dev/md/BigBlue:0 and /dev/md0 - cannot decide
> which to use.

Please show the output of your mdadm.conf file, and the complete command
you used to assemble with.  Add "-v" to it to show more information.

{There's nothing wrong with your array, just conflicting info in your
configuration file.}

Phil

Re: Reassemble Raid 6

[Phil Turmel]

On 02/10/2014 07:13 PM, Justin Stephenson wrote:
> Hello Phil,
> 
> You are 100% correct. Thanks for your email. I had 2 separate ARRAY
> entries in my mdadm.config file. When I added the spare, I added the new
> information to the config file but did not remove the old entry. Total
> newbie mistake.
> 
> - I commented out all the previous entries in the mdadm.config file (it
> had a devices lists instead of the UUID information)
> 
> - I successfully assembled the array (mdadm --assemble /dev/md0 
> /dev/sdb1 etc...)
> 
> - I  updated the config file using the information from mdadm -Esc
> partitions | grep UUID and deleted the old entries.
> 
> - I uncommented the fstab entry for the array and rebooted.
> 
> 
> Everything is working perfectly now.
> 
> 
> I remember reading somewhere that mdadm can run without the config file
> by using the RAID uuid and the information in the superblocks. Would
> this be more reliable?
> 
> Thanks Again

You're welcome.

I suggest you trim the mdadm.conf file even further--I only specify name
and uuid, so device changes don't interfere with assembly.  Like so
(slightly edited):

MAILFROM mdadm@example.com
MAILADDR philip@example.com

DEVICE /dev/sd[a-z][1-9]

# Mirrored Boot partitions
ARRAY /dev/md1 UUID=75c011c6:caeb06ea:ec7e3370:aa4f3320

# Far mirror (Raid10) core operations
ARRAY /dev/md2 UUID=6b4858da:f24e2567:34e73fe5:b8f2c118

# Bulk redundant (Raid6) storage
ARRAY /dev/md3 UUID=04f3706c:79a3cd73:8a558eee:93ec1879


HTH,

Phil

ps. Don't forget to update your initramfs after any changes to mdadm.conf!

Re[2]: Reassemble Raid 6

[Justin Stephenson]

Hello Phil,

You are 100% correct. Thanks for your email. I had 2 separate ARRAY 
entries in my mdadm.config file. When I added the spare, I added the new 
information to the config file but did not remove the old entry. Total 
newbie mistake.

- I commented out all the previous entries in the mdadm.config file (it 
had a devices lists instead of the UUID information)

- I successfully assembled the array (mdadm --assemble /dev/md0  
/dev/sdb1 etc...)

- I  updated the config file using the information from mdadm -Esc 
partitions | grep UUID and deleted the old entries.

- I uncommented the fstab entry for the array and rebooted.


Everything is working perfectly now.


I remember reading somewhere that mdadm can run without the config file 
by using the RAID uuid and the information in the superblocks. Would 
this be more reliable?

Thanks Again,

- Justin

------ Original Message ------
From: "Phil Turmel" <philip@turmel.org>
To: "Justin Stephenson" <justin@evensteveninc.com>; 
linux-raid@vger.kernel.org
Sent: 10/02/2014 12:53:31 PM
Subject: Re: Reassemble Raid 6

>On 02/10/2014 11:48 AM, Justin Stephenson wrote:
>>  Hello,
>>
>>  I have reviewed the Linux Raid Wiki regarding rebuilding and it
>>  recommended writing a note to the list.
>>
>>  I am running an mdadm raid on CENTOS 6.5 with 6 disks in a Raid 6 off 
>>of
>>  my motherboard's SATA controller.
>>
>>  I added a 7th disk as a spare.
>>
>>  When I rebooted the raid after adding the spare, it would not mount 
>>and
>>  the OS would only boot into recovery mode. I changed my fsck file to
>>  exclude the raid and can now boot into the GUI.
>>
>>  I have tried to reassemble the array using --assemble and I get the 
>>the
>>  following message:
>>
>>  mdadm: we match both /dev/md/BigBlue:0 and /dev/md0 - cannot decide
>>  which to use.
>
>Please show the output of your mdadm.conf file, and the complete 
>command
>you used to assemble with. Add "-v" to it to show more information.
>
>{There's nothing wrong with your array, just conflicting info in your
>configuration file.}
>
>Phil