Reshape RAID10 -> RAID1

Reshape RAID10 -> RAID1

[Charles Polisher]

Hi all,

I hope to reshape a RAID10 (near,2) with 2 failed and physically
removed members [_U_U] into a RAID1 hopefully [UU], for the
benefit of seeing a healthy status.

Is following proposed invocation correct?

   mdadm --grow /dev/md2 --level=1

Details:

root@mencius $ mdadm --query --verbose --detail /dev/md2
/dev/md2:
        Version : 1.1
  Creation Time : Fri Jul 15 22:56:53 2011
     Raid Level : raid10
     Array Size : 1944916992 (1854.82 GiB 1991.59 GB)
  Used Dev Size : 972458496 (927.41 GiB 995.80 GB)
   Raid Devices : 4
  Total Devices : 2
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Tue Feb 25 22:00:46 2014
          State : active, degraded 
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

         Layout : near=2
     Chunk Size : 512K

           Name : localhost.localdomain:2
           UUID : 971ee8b2:8d980355:0e5dfae9:c8bccd89
         Events : 5326341

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       8       19        1      active sync   /dev/sdb3
       2       0        0        2      removed
       3       8        3        3      active sync   /dev/sda3
root@mencius $ uname -a
Linux mencius 2.6.32-358.18.1.el6.centos.plus.x86_64 #1 SMP Wed Aug 28 16:14:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
root@mencius $ mdadm --version
mdadm - v3.2.6 - 25th October 2012


Thanks,
-- 
Charles Polisher

Re: Reshape RAID10 -> RAID1

[NeilBrown]

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On Tue, 25 Feb 2014 22:05:32 -0800 Charles Polisher <cpolish@surewest.net>
wrote:

> Hi all,
> 
> I hope to reshape a RAID10 (near,2) with 2 failed and physically
> removed members [_U_U] into a RAID1 hopefully [UU], for the
> benefit of seeing a healthy status.
> 
> Is following proposed invocation correct?
> 
>    mdadm --grow /dev/md2 --level=1

I think so.  If not, mdadm will complain.

It is quite easy to experiment: create some largish file, use losetup to turn
them into block device.  Then experiment with /dev/loop*

NeilBrown


> 
> Details:
> 
> root@mencius $ mdadm --query --verbose --detail /dev/md2
> /dev/md2:
>         Version : 1.1
>   Creation Time : Fri Jul 15 22:56:53 2011
>      Raid Level : raid10
>      Array Size : 1944916992 (1854.82 GiB 1991.59 GB)
>   Used Dev Size : 972458496 (927.41 GiB 995.80 GB)
>    Raid Devices : 4
>   Total Devices : 2
>     Persistence : Superblock is persistent
> 
>   Intent Bitmap : Internal
> 
>     Update Time : Tue Feb 25 22:00:46 2014
>           State : active, degraded 
>  Active Devices : 2
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 0
> 
>          Layout : near=2
>      Chunk Size : 512K
> 
>            Name : localhost.localdomain:2
>            UUID : 971ee8b2:8d980355:0e5dfae9:c8bccd89
>          Events : 5326341
> 
>     Number   Major   Minor   RaidDevice State
>        0       0        0        0      removed
>        1       8       19        1      active sync   /dev/sdb3
>        2       0        0        2      removed
>        3       8        3        3      active sync   /dev/sda3
> root@mencius $ uname -a
> Linux mencius 2.6.32-358.18.1.el6.centos.plus.x86_64 #1 SMP Wed Aug 28 16:14:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> root@mencius $ mdadm --version
> mdadm - v3.2.6 - 25th October 2012
> 
> 
> Thanks,


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Re: Reshape RAID10 -> RAID1

[Charles Polisher]

On Wed, Feb 26, 2014 at 06:03:17PM +1100, NeilBrown wrote:
> On Tue, 25 Feb 2014 22:05:32 -0800 Charles Polisher <cpolish@surewest.net>
> wrote:
> 
> > Hi all,
> > 
> > I hope to reshape a RAID10 (near,2) with 2 failed and physically
> > removed members [_U_U] into a RAID1 hopefully [UU], for the
> > benefit of seeing a healthy status.
> > 
> > Is following proposed invocation correct?
> > 
> >    mdadm --grow /dev/md2 --level=1
> 
> I think so.  If not, mdadm will complain.
> 
> It is quite easy to experiment: create some largish file, use losetup to turn
> them into block device.  Then experiment with /dev/loop*

Thanks! Will do exactly that.
-- 
Charles