Undestanding /proc/mdstat with raid10

Undestanding /proc/mdstat with raid10

[Sebastian Muniz]

Hello,
I have searched a lot trying to answer this.
I have a raid10 array on an openfiler box.
Personalities : [raid10]
md0 : active raid10 sde1[3] sdd1[2] sdc1[1] sdb1[0]
       181760 blocks super 1.2 64K chunks 2 near-copies [4/4] [UUUU]

unused devices: <none>
Actually this is a Virtualbox machine with the same disk setup. I made 6 
x 100 Mbytes disks for the test.

How can I tell which disks are mirrored?

My goal is to free the two mirror disks from md0, add two more free 
disks, create a new md1 raid5 array, and move the contents from md0 to md1

Thanks in advance.
Sebastian

PS: in case it is relevant, i am adding the detailed md0 output.

[root@of ~]# mdadm --misc --detail /dev/md0
/dev/md0:
         Version : 1.2
   Creation Time : Tue Aug  9 03:01:14 2011
      Raid Level : raid10
      Array Size : 181760 (177.53 MiB 186.12 MB)
   Used Dev Size : 90880 (88.76 MiB 93.06 MB)
    Raid Devices : 4
   Total Devices : 4
     Persistence : Superblock is persistent

     Update Time : Tue Aug  9 03:20:06 2011
           State : clean
  Active Devices : 4
Working Devices : 4
  Failed Devices : 0
   Spare Devices : 0

          Layout : near=2
      Chunk Size : 64K

            Name : of:0  (local to host of)
            UUID : 63b2145a:49030744:41b8f5b4:cb11bc1d
          Events : 19

     Number   Major   Minor   RaidDevice State
        0       8       17        0      active sync   /dev/sdb1
        1       8       33        1      active sync   /dev/sdc1
        2       8       49        2      active sync   /dev/sdd1
        3       8       65        3      active sync   /dev/sde1

Re: Undestanding /proc/mdstat with raid10

[Torbjørn Skagestad]

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On Tue, 2011-08-09 at 04:14 -0300, Sebastian Muniz wrote:
> Hello,
> I have searched a lot trying to answer this.
> I have a raid10 array on an openfiler box.
> Personalities : [raid10]
> md0 : active raid10 sde1[3] sdd1[2] sdc1[1] sdb1[0]
>        181760 blocks super 1.2 64K chunks 2 near-copies [4/4] [UUUU]
> 
> unused devices: <none>
> Actually this is a Virtualbox machine with the same disk setup. I made 6 
> x 100 Mbytes disks for the test.
> 
> How can I tell which disks are mirrored?
That depends on the layout of your array. raid10 is not raid1+0
> 
> My goal is to free the two mirror disks from md0, add two more free 
> disks, create a new md1 raid5 array, and move the contents from md0 to md1
> 
> Thanks in advance.
> Sebastian
> 
> PS: in case it is relevant, i am adding the detailed md0 output.
> 
> [root@of ~]# mdadm --misc --detail /dev/md0
> /dev/md0:
>          Version : 1.2
>    Creation Time : Tue Aug  9 03:01:14 2011
>       Raid Level : raid10
>       Array Size : 181760 (177.53 MiB 186.12 MB)
>    Used Dev Size : 90880 (88.76 MiB 93.06 MB)
>     Raid Devices : 4
>    Total Devices : 4
>      Persistence : Superblock is persistent
> 
>      Update Time : Tue Aug  9 03:20:06 2011
>            State : clean
>   Active Devices : 4
> Working Devices : 4
>   Failed Devices : 0
>    Spare Devices : 0
> 
>           Layout : near=2
                    ^^^^^^
This layout is described at
http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10

Assuming the info there is correct, mirrored devices are [0,1] and [2,3]

>       Chunk Size : 64K
> 
>             Name : of:0  (local to host of)
>             UUID : 63b2145a:49030744:41b8f5b4:cb11bc1d
>           Events : 19
> 
>      Number   Major   Minor   RaidDevice State
>         0       8       17        0      active sync   /dev/sdb1
>         1       8       33        1      active sync   /dev/sdc1
>         2       8       49        2      active sync   /dev/sdd1
>         3       8       65        3      active sync   /dev/sde1
> --
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-- 
Torbjørn Skagestad
Idé Til Produkt AS
torborn@itpas.no

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