On Thursday November 12, janek_listy@xxxxx 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which has been withdrawn.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
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