On Mon, 24 Oct 2011 17:03:46 +0100 Michael Busby [off-list ref]
wrote:

should the speed be very slow when doing this progress, its a lot
slower than a normal grow

Yes.
The array is being reshaped in-place.  i.e. data is being read from part of
the array, rearranged, and written back to the same part of the array.
As you can imagine, this is risky - a crash will leave an inconsistent state.
Hence the backup file.  Everything in the array is first written to the
backup file, then back to the array.  So it is slow.

A "normal" grow is writing to somewhere where there is no valid data, so it
doesn't need the backup.

I do have a plan to make this faster.... but I have lots of plans and little
time.

NeilBrown

reshape =  1.2% (25006080/1953513984) finish=12481.8min speed=2574K/sec

On 24 October 2011 15:11, Mathias Burén [off-list ref] wrote:

quoted

On 24 October 2011 14:11, Michael Busby [off-list ref] wrote:

quoted

At the moment i have a raid5 setup with 5 disks, i am looking to add a
6th disk and change from raid 5 to raid 6

having looked at Neil's site i have found the following command, and
just want to double check this is still the recommend way of
converting

mdadm --grow /dev/md0 --level=6 --raid-disks=6 --backup-file=/home/md.backup

also would i need to add the extra disk before or after the command?

cheers
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Hi,

I grew my 6 disk RAID5 to a 7 disk RAID6. First, add the drive. Then
partition it as required. Then add the drive to the array (I think
it'll become a spare?). Then you can grow it.

Make sure you're using the latest mdadm tools available.

Regards,
Mathias

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