Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

[Janek Kozicki]

Hi,

I have an old debian etch backup server. It has 5 drives in raid4.
I want to add a sixth drive to jump to raid6. I don't want to upgrade
debian etch, because the server is working real fine, and doing an
upgrade would be too much problems.

Here it is:

  backup:~# uname -a
  Linux backup 2.6.24-etchnhalf.1-686 #1 SMP Sat Aug 15 16:51:49 UTC 2009 i686 GNU/Linux

  backup:~# mdadm -D /dev/md1
/dev/md1:
        Version : 01.01.03
  Creation Time : Fri Nov  2 23:35:37 2007
     Raid Level : raid5
     Array Size : 1933614592 (1844.04 GiB 1980.02 GB)
    Device Size : 966807296 (461.01 GiB 495.01 GB)
   Raid Devices : 5
  Total Devices : 5
Preferred Minor : 1
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Thu Nov 12 21:59:15 2009
          State : active
 Active Devices : 5
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 128K

           Name : backup:1  (local to host backup)
           UUID : 22f22c35:99613d52:31d407a6:55bdeb84
         Events : 718938

    Number   Major   Minor   RaidDevice State
       5      22        3        0      active sync   /dev/hdc3
       1       8        3        1      active sync   /dev/sda3
       3       3        3        2      active sync   /dev/hda3
       4       8       35        3      active sync   /dev/sdc3
       6       8       19        4      active sync   /dev/sdb3
backup:~# 


And so my plan is to get some liveCD with 2.6.31 (or maybe 2.6.32 ?).
Connect the sixth drive, boot liveCD, perform the migration:

mdadm --add /dev/md2 /dev/sdd3
mdadm --grow /dev/md2 --level=raid6 --raid-disks=6

Then reboot back into linux 2.6.24.

Will this work?

Will 2.6.24 understand such raid6 ?

thanks a lot for your help
-- 
Janek Kozicki                                                         |

Re: Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

[Janek Kozicki]

Janek Kozicki said:     (by the date of Thu, 12 Nov 2009 22:03:51 +0100)

> I have an old debian etch backup server. It has 5 drives in raid4.
                                                              ^^^^^

oops. a typo, should be "raid5" of course:

I have an old debian etch backup server. It has 5 drives in raid5.
                                                            ^^^^^^

-- 
Janek Kozicki                                                         |

Re: Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

[Robin Hill]

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On Thu Nov 12, 2009 at 10:03:51PM +0100, Janek Kozicki wrote:

> Hi,
> 
> I have an old debian etch backup server. It has 5 drives in raid4.
> I want to add a sixth drive to jump to raid6. I don't want to upgrade
> debian etch, because the server is working real fine, and doing an
> upgrade would be too much problems.
> 
> And so my plan is to get some liveCD with 2.6.31 (or maybe 2.6.32 ?).
> Connect the sixth drive, boot liveCD, perform the migration:
> 
> mdadm --add /dev/md2 /dev/sdd3
> mdadm --grow /dev/md2 --level=raid6 --raid-disks=6
> 
> Then reboot back into linux 2.6.24.
> 
> Will this work?
> 
> Will 2.6.24 understand such raid6 ?
> 
I don't think so, no.  It's not a standard RAID6 (as all the Q parity is
on a single disk) so I think you need the newer kernel to understand it.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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Re: Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

[Neil Brown]

On Thursday November 12, janek_listy@wp.pl wrote:
> Hi,
> 
> I have an old debian etch backup server. It has 5 drives in raid4.
> I want to add a sixth drive to jump to raid6. I don't want to upgrade
> debian etch, because the server is working real fine, and doing an
> upgrade would be too much problems.
> 
> Here it is:
> 
>   backup:~# uname -a
>   Linux backup 2.6.24-etchnhalf.1-686 #1 SMP Sat Aug 15 16:51:49 UTC 2009 i686 GNU/Linux
> 
>   backup:~# mdadm -D /dev/md1
> /dev/md1:
>         Version : 01.01.03
>   Creation Time : Fri Nov  2 23:35:37 2007
>      Raid Level : raid5
>      Array Size : 1933614592 (1844.04 GiB 1980.02 GB)
>     Device Size : 966807296 (461.01 GiB 495.01 GB)
>    Raid Devices : 5
>   Total Devices : 5
> Preferred Minor : 1
>     Persistence : Superblock is persistent
> 
>   Intent Bitmap : Internal
> 
>     Update Time : Thu Nov 12 21:59:15 2009
>           State : active
>  Active Devices : 5
> Working Devices : 5
>  Failed Devices : 0
>   Spare Devices : 0
> 
>          Layout : left-symmetric
>      Chunk Size : 128K
> 
>            Name : backup:1  (local to host backup)
>            UUID : 22f22c35:99613d52:31d407a6:55bdeb84
>          Events : 718938
> 
>     Number   Major   Minor   RaidDevice State
>        5      22        3        0      active sync   /dev/hdc3
>        1       8        3        1      active sync   /dev/sda3
>        3       3        3        2      active sync   /dev/hda3
>        4       8       35        3      active sync   /dev/sdc3
>        6       8       19        4      active sync   /dev/sdb3
> backup:~# 
> 
> 
> And so my plan is to get some liveCD with 2.6.31 (or maybe 2.6.32 ?).
> Connect the sixth drive, boot liveCD, perform the migration:
> 
> mdadm --add /dev/md2 /dev/sdd3
> mdadm --grow /dev/md2 --level=raid6 --raid-disks=6
> 
> Then reboot back into linux 2.6.24.
> 
> Will this work?

In principle, yes.
However:
  1/ you need linux 2.6.32 (not yet released).  Don't try with 2.6.31
  2/ you need mdadm 3.1.1 (not yet released).  Don't try with 3.1,
     which has been withdrawn.
  3/ You need a "--backup-file=/some/file" argument.  The /some/file
     must be on a different device.
  
> 
> Will 2.6.24 understand such raid6 ?

Yes.
  mdadm will first convert the RAID5 to a RAID6 in which the Q blocks
  are all on the last disk.  This is done instantly.
  Then mdadm will start and manage a process of re-laying out each
  stripe to have the Q blocks rotated around the various devices.
  This will take a while, approximately 1 day.  Once this is complete,
  you can then access the array from 2.6.24.

NeilBrown

Re: Using 2.6.31 liveCD to grow (reshape) raid5 into raid6, then bacck to old kernel?

[Janek Kozicki]

Neil Brown said:     (by the date of Fri, 13 Nov 2009 15:37:05 +1100)

> > And so my plan is to get some liveCD with 2.6.31 (or maybe 2.6.32 ?).
> > Connect the sixth drive, boot liveCD, perform the migration:
> > 
> > mdadm --add /dev/md2 /dev/sdd3
> > mdadm --grow /dev/md2 --level=raid6 --raid-disks=6
> > 
> > Then reboot back into linux 2.6.24.
> > 
> > Will this work?
> 
> In principle, yes.
> However:
>   1/ you need linux 2.6.32 (not yet released).  Don't try with 2.6.31
>   2/ you need mdadm 3.1.1 (not yet released).  Don't try with 3.1,
>      which has been withdrawn.
>   3/ You need a "--backup-file=/some/file" argument.  The /some/file
>      must be on a different device.
>   
> > 
> > Will 2.6.24 understand such raid6 ?
> 
> Yes.
>   mdadm will first convert the RAID5 to a RAID6 in which the Q blocks
>   are all on the last disk.  This is done instantly.
>   Then mdadm will start and manage a process of re-laying out each
>   stripe to have the Q blocks rotated around the various devices.
>   This will take a while, approximately 1 day.  Once this is complete,
>   you can then access the array from 2.6.24.
> 
> NeilBrown


Great, thanks a lot! I'm not in such a hurry - I will wait until they
are released.


-- 
Janek Kozicki                                                         |