Perhaps also worth noting -- "mdadm -D /dev/md0" does not output the
stanza with Name, UUID and Events.  Expected?

On Sun, Jan 12, 2014 at 11:42 PM, Richard Michael
[off-list ref] wrote:

Following up my own message, I forgot to include mdadm and kernel versions:

$ mdadm --version
mdadm - v3.3 - 3rd September 2013

$ uname -a
Linux anvil.localdomain 3.12.6-300.fc20.x86_64 #1 SMP Mon Dec 23
16:44:31 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux



On Sun, Jan 12, 2014 at 11:37 PM, Richard Michael
[off-list ref] wrote:

quoted

Hello list,

I grew a RAID0 by one-disk, and it re-shaped via RAID4 as expected.

However, the component superblocks still RAID4, while /proc/mdstat,
/sys/block/md0/md/level and "mdadm -D" all indicate RAID0.

I am reluctant to stop the array, in case auto-assemble can't put it
back together.  (I suppose I could create a new array, but I'd want to
be quite confident about the layout of the disks.)


Is this a bug?  Should/can I re-write the superblock(s)?


# cat /proc/mdstat
Personalities : [raid0] [raid1] [raid6] [raid5] [raid4]
md0 : active raid0 sdc1[2] sdd1[0]
      5860268032 blocks super 1.2 512k chunks

# cat /sys/block/md0/md/level
raid0

# mdadm -D /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Fri Jan 10 13:02:25 2014
     Raid Level : raid0
     Array Size : 5860268032 (5588.79 GiB 6000.91 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Sun Jan 12 20:08:53 2014
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

     Chunk Size : 512K

    Number   Major   Minor   RaidDevice State
       0       8       49        0      active sync   /dev/sdd1
       2       8       33        1      active sync   /dev/sdc1



But,


# mdadm -E /dev/sd[cd]1
/dev/sdc1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 8f51352a:610d0ecd:a1e28ddd:86c8586c
           Name : anvil.localdomain:0  (local to host anvil.localdomain)
  Creation Time : Fri Jan 10 13:02:25 2014
     Raid Level : raid4
   Raid Devices : 3

 Avail Dev Size : 5860268943 (2794.39 GiB 3000.46 GB)
     Array Size : 5860268032 (5588.79 GiB 6000.91 GB)
  Used Dev Size : 5860268032 (2794.39 GiB 3000.46 GB)
    Data Offset : 260096 sectors
   Super Offset : 8 sectors
   Unused Space : before=260008 sectors, after=2959 sectors
          State : clean
    Device UUID : ad6e6c88:0f897bc1:1f6ec909:f599bc01

    Update Time : Sun Jan 12 20:08:53 2014
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : 1388a7b - correct
         Events : 9451

     Chunk Size : 512K

   Device Role : Active device 1
   Array State : AA. ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdd1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 8f51352a:610d0ecd:a1e28ddd:86c8586c
           Name : anvil.localdomain:0  (local to host anvil.localdomain)
  Creation Time : Fri Jan 10 13:02:25 2014
     Raid Level : raid4
   Raid Devices : 3

 Avail Dev Size : 5860268032 (2794.39 GiB 3000.46 GB)
     Array Size : 5860268032 (5588.79 GiB 6000.91 GB)
    Data Offset : 260096 sectors
   Super Offset : 8 sectors
   Unused Space : before=260008 sectors, after=2959 sectors
          State : clean
    Device UUID : b3cda274:547919b1:4e026228:0a4981e7

    Update Time : Sun Jan 12 20:08:53 2014
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : e16a1979 - correct
         Events : 9451

     Chunk Size : 512K

   Device Role : Active device 0
   Array State : AA. ('A' == active, '.' == missing, 'R' == replacing)



Somewhat aside, I grew the array with:

"mdadm --grow /dev/md0 --raid-devices=2 --add /dev/sdc1"

I suspect I should not have used "--add".  Looking at the superblock,
there is a 3rd unknown device, which I did not intend to add.

Did I convince mdadm to add two devices at the same time, sdc1 *and* a
missing device?  (This surprises me a bit, in the sense that
--raid-devices=2 would pertain to the added devices, rather than the
total devices in the array.)

Or, perhaps mdadm add a "dummy" device as part of the temporary RAID4
conversion?


Thanks for any comments.

Regards,
Richard