Re: Can't grow IMSM RAID5

"nixbugz" <nixbugz@xxxxxxxxxxx> · Tue, 1 Apr 2014 18:34:07 +0100

-----Original Message----- 
From: Jiang, Dave
Sent: Tuesday, April 1, 2014 5:08 PM
To: nixbugz@xxxxxxxxxxx
Cc: linux-raid@xxxxxxxxxxxxxxx ; Paszkiewicz, Artur
Subject: Re: Can't grow IMSM RAID5

On Tue, 2014-04-01 at 16:42 +0100, nixbugz wrote:
Hello

I’m stuck trying to add a 4th disc to an IMSM RAID5 container:

# mdadm -a /dev/md127 /dev/sdb
mdadm: added /dev/sdb

# mdadm --grow --raid-devices=4
/dev/md127 --backup-file=/mnt/spare/raid-backup-file
mdadm: Cannot read superblock for /dev/md127

I think you need to grow the RAID volume and not the container? So it
would be /dev/md0 or /dev/md1 instead of /dev/md127? Here's URL to the
Linux IMSM user's manual that hopefully may be of use:
http://www.intel.com/support/chipsets/rste/sb/CS-033622.htm

# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdd[2] sda[1] sdc[0]
      1887436800 blocks super external:/md127/0 level 5, 128k chunk,
algorithm 0 [3/3] [UUU]

md1 : active (auto-read-only) raid5 sdc[2] sdd[1] sda[0]
      66077696 blocks super external:/md127/1 level 5, 128k chunk, 
algorithm
0 [3/3] [UUU]

md127 : inactive sdb[3](S) sda[2](S) sdc[1](S) sdd[0](S)
      12612 blocks super external:imsm

unused devices: <none>

# mdadm –V
mdadm - v3.3 - 3rd September 2013

I don’t know if this is related but mdmon has trouble finding the ports:

# mdadm --detail-platform -v
mdadm: checking metadata 0.90
mdadm: 0.90 metadata is platform independent
mdadm: checking metadata 1.x
mdadm: 1.x metadata is platform independent
mdadm: checking metadata ddf
mdadm: ddf metadata is platform independent
mdadm: checking metadata imsm
mdmon: found Intel(R) SATA RAID controller at 0000:00:1f.2.
       Platform : Intel(R) Matrix Storage Manager
        Version : 11.6.0.1702
    RAID Levels : raid0 raid1 raid10 raid5
    Chunk Sizes : 4k 8k 16k 32k 64k 128k
    2TB volumes : supported
      2TB disks : supported
      Max Disks : 6
    Max Volumes : 2 per array, 4 per controller
I/O Controller : /sys/devices/pci0000:00/0000:00:1f.2 (SATA)
mdmon: failed to determine port number for
/sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0
mdmon: failed to enumerate ports on SATA controller at 0000:00:1f.2.
mdadm: checking metadata mbr
mdadm: mbr metadata is platform independent
mdadm: checking metadata gpt
mdadm: gpt metadata is platform independent
#

Artur, any ideas why mdmon isn't happy in this instance?

Thanks

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Thanks for your quick response.  I wasn't sure whether to grow container or 
volume but this from man mdadm decided it:

     Using  GROW  on containers is currently supported only for Intel's 
IMSM
     container format.   The  number  of  devices  in  a  container  can 
be
     increased  - which affects all arrays in the container ...

It gives the same message anyway when applied to the volume md0.

This extract from the Intel doc you linked to says the same (note that md0 
is the container here :-)

   The example below adds a single disk to the RAID container and then 
grows the
   volume(s). Because IMSM volumes inside a container must span the same
   number of disks, all volumes are expanded.
...
       mdadm –a /dev/md0 /dev/sde
       mdadm –G /dev/md0 –n 4 --backup-file=/tmp/backup

Might it be something to do with what's already on the new drive?
This is an Intel DQ77MK motherboard.

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