Sorry to bring up a old thread, last night i had a power cut and this
morning when the power has come back i have tried to boot the server,
but the raid will not assemble on using a live CD i have found that
one of the disk is reporting "possibly out of date" is there any way
to force this disk back in? the bigger problem i have is that my
external caddie has died so i was running a degraded raid 6 but now it
is only starting with 4 out of 6 devices. is there anyway to get this
back?

i have though about recreating the array using the --assume-clean
option but not sure if that's a good idea

any help will be much appreciated



On 24 October 2011 21:47, Michael Busby [off-list ref] wrote:

I was sure i added the device before, but when rebooted the system it
has seemed to lose the extra drive and i had already restarted the
grow command with out checking the disk was there, so more than likely
a mistake by me



On 24 October 2011 21:39, NeilBrown [off-list ref] wrote:

quoted

On Mon, 24 Oct 2011 21:19:22 +0100 Michael Busby [off-list ref]
wrote:

quoted

Ok thanks, i have 1 small issue, when added the extra disk its been
maked as spare, is this normal?

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : active raid6 sde[0] sdg[6](S) sda[4] sdb[3] sdd[2] sdc[1]
      7814055936 blocks super 1.0 level 6, 512k chunk, algorithm 18
[6/5] [UUUUU_]
      [>....................]  reshape =  3.0% (59244544/1953513984)
finish=11122.8min speed=2837K/sec

It looks like the extra drive was added after you started the grow.

So it is still a spare.
Once the grow finishes you will have a singly-degraded RAID6.
Then it will immediately start recovering the missing device to the spare.

Did you add the extra drive after starting the grow - or before??

NeilBrown

quoted

quoted

On 24 October 2011 21:14, NeilBrown [off-list ref] wrote:

quoted

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

quoted

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

quoted

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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