On Mon Dec 21, 2009 at 03:41:33AM +0000, Kristleifur Daðason wrote:

quoted

Hi all,

I wish to convert my 3-drive RAID-5 array to a 6-drive RAID-6. I'm on
Linux 2.6.32.2 and have mdadm version 3.1.1 with the 32-bit-array-size
patch from here: http://osdir.com/ml/linux-raid/2009-11/msg00534.html

I have three live drives and three spares added to the array. When I
initialize the command, mdadm does the initial checks and aborts with
a "cannot set device shape" without doing anything to the array.

$ mdadm --grow /dev/md_d1 --level=6 --raid-devices=6
--backup-file=/root/backup.md1_to_r6
mdadm: metadata format 1.10 unknown, ignored.
mdadm: metadata format 1.10 unknown, ignored.
mdadm level of /dev/md_d1 changed to raid6
mdadm: Need to backup 1024K of critical section..
mdadm: Cannot set device shape for /dev/md_d1
mdadm: aborting level change

On Mon, Dec 21, 2009 at 7:25 AM, Michael Evans [off-list ref] wrote:

This is odd; cat /proc/mdstat shows 1.0 and 1.1 for my metadata
formats; however using --detail --scan  I _DO_ see 1.00 and 1.01 on my
system.

On Mon, Dec 21, 2009 at 9:35 AM, Robin Hill [off-list ref] wrote:

I don't think you can grow and reshape simultaneously.  I think you'll
need to do this as two operations - either grow to a 5 disk RAID5 then
reshape to a 6 disk RAID6, or reshape to a 4 disk RAID6 then grow.

Thanks for the replies, Michael and Robin.

Re. metadata version number discrepancy, I'm going to assume for now
that it doesn't affect my reshape, and take it up later in its own
list thread.

Robin, it makes sense that I can't actually grow and reshape
simultaneously - it fits to the mdadm halt I'm seeing - but I did note
Neil Brown saying here >> http://neil.brown.name/blog/20090817000931
<< that

--- "One way to avoid the extra cost of doing the backup [reshape] is

to increase the number of devices at the same time. e.g. if you had a
4-drive RAID5 you could convert it to a 6-drive RAID6 with a command
like mdadm --grow /dev/md0 --level=6 --raid-disk=6 then it will
combine the increase in the number of devices with the change to the
layout and will copy every block only once. " ---

I'm OK with doing the grow and reshape in two separate steps, but the
indication that it should be possible in one step makes me a bit
anxious about the health of my array as it is now. Can anyone confirm
/ deny that a simultaneous reshape+grow is possible or not? Anyone
done one? :)

Thanks!

-- Kristleifur
-- Kristleifur
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