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Thread: RAID starting at md127 instead of md0

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  1. #1
    Join Date
    Apr 2008
    Beans
    18

    RAID starting at md127 instead of md0

    I have recently created a RAID 5 array under Ubuntu 11.04 and am having some trouble getting it to assemble correctly on system boot. So far after every boot the array assembles correctly but in read-only mode at /dev/md127. Stopping this array and running:

    Code:
    mdadm --assemble --scan
    will correctly mount the array at /dev/md0. My mdadm.conf file:

    Code:
    DEVICE partitions
    ARRAY /dev/md/0 metadata=1.2 name=nagelnas:0 UUID=e4665ceb:15f8e4b6:b186d497:7d365254
    detail of the array:

    Code:
    sudo mdadm --detail /dev/md0
    
    /dev/md0:
            Version : 1.2
      Creation Time : Sun May 15 22:39:38 2011
         Raid Level : raid5
         Array Size : 5860544512 (5589.05 GiB 6001.20 GB)
      Used Dev Size : 1465136128 (1397.26 GiB 1500.30 GB)
       Raid Devices : 5
      Total Devices : 5
        Persistence : Superblock is persistent
    
        Update Time : Sun May 22 09:52:09 2011
              State : clean
     Active Devices : 5
    Working Devices : 5
     Failed Devices : 0
      Spare Devices : 0
    
             Layout : left-symmetric
         Chunk Size : 512K
    
               Name : nagelnas:0  (local to host nagelnas)
               UUID : e4665ceb:15f8e4b6:b186d497:7d365254
             Events : 18
    
        Number   Major   Minor   RaidDevice State
           0       8        0        0      active sync   /dev/sda
           1       8       16        1      active sync   /dev/sdb
           2       8       32        2      active sync   /dev/sdc
           3       8       48        3      active sync   /dev/sdd
           5       8       64        4      active sync   /dev/sde
    
    
    cat /proc/mdstat
    
    Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
    md0 : active raid5 sda[0] sde[5] sdd[3] sdc[2] sdb[1]
          5860544512 blocks super 1.2 level 5, 512k chunk, algorithm 2 [5/5] [UUUUU]
          
    unused devices: <none>
    examine of one of the disks in the array:

    Code:
    sudo mdadm --examine /dev/sda
    
    /dev/sda:
              Magic : a92b4efc
            Version : 1.2
        Feature Map : 0x0
         Array UUID : e4665ceb:15f8e4b6:b186d497:7d365254
               Name : nagelnas:0  (local to host nagelnas)
      Creation Time : Sun May 15 22:39:38 2011
         Raid Level : raid5
       Raid Devices : 5
    
     Avail Dev Size : 2930273007 (1397.26 GiB 1500.30 GB)
         Array Size : 11721089024 (5589.05 GiB 6001.20 GB)
      Used Dev Size : 2930272256 (1397.26 GiB 1500.30 GB)
        Data Offset : 2048 sectors
       Super Offset : 8 sectors
              State : clean
        Device UUID : 922f3fc5:b9078b42:86230bc3:b8abfc7e
    
        Update Time : Sun May 22 09:51:29 2011
           Checksum : 5274f4ec - correct
             Events : 18
    
             Layout : left-symmetric
         Chunk Size : 512K
    
       Device Role : Active device 0
       Array State : AAAAA ('A' == active, '.' == missing)

    Any idea what I am doing wrong here? Not the biggest deal in the world to assemble the array by hand but still something I want to have happen automatically.

    Thanks,
    Andrew

  2. #2
    Join Date
    Apr 2008
    Beans
    18

    Re: RAID starting at md127 instead of md0

    Some additional information, after boot the status of the array is:

    Code:
    cat /proc/mdstat 
    
    Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
    md127 : active (auto-read-only) raid5 sdc[2] sdd[3] sde[5] sdb[1] sda[0]
          5860544512 blocks super 1.2 level 5, 512k chunk, algorithm 2 [5/5] [UUUUU]
          
    unused devices: <none>

  3. #3
    Join Date
    Dec 2010
    Beans
    7

    Re: RAID starting at md127 instead of md0

    I'm having exactly the same problems as you. I was running 10.10 with a RAID5 set as md0. Been working fine for ages. I upgraded to 11.04 and my raid is now appearing at md127.

    I have to stop the raid, run assemble which puts it back to md0 and I can then mount it.

  4. #4
    Join Date
    May 2011
    Beans
    3

    Re: RAID starting at md127 instead of md0

    Thought I would post here to say that I had this same problem with ubuntu 11.04 -generic

    With the -server kernel installed however, (11.04) works fine, for anyone who finds this thread.

  5. #5
    Join Date
    Jan 2008
    Location
    UK
    Beans
    15

    Re: RAID starting at md127 instead of md0

    I have exactly the same problem on Fedora 13:
    uname -a
    *** 2.6.34.8-68.fc13.x86_64 #1 SMP ***
    Curiously, I tried changing /etc/fstab to mount /dev/md127 rather than what I originally had /dev/md0 and I still got the boot message:
    Mounting local filesystems: mount: special device /dev/md0 does not exist

  6. #6
    Join Date
    Oct 2009
    Beans
    2,199
    Distro
    Ubuntu 10.10 Maverick Meerkat

    Re: RAID starting at md127 instead of md0

    Hi all.
    This seems to be a "feature" of the mdadm in the newest kernel. There was another thread with similar symptoms recently.
    For reasons I do not yet understand, mdadm seems to invent an array device name out of thin air when there is a problem. This confuses everybody. md127 seems to be a common name it now chooses.

    Two things seem to be important:

    1) The ARRAY statement in mdadm.conf needs to be correct. I am not convinced the direct output of mdadm -Es is reliable anymore. Especially the name directive. Mine broke because I had a space in the name!
    So I would try minimizing the specifiers in your ARRAY statements: all you normally need is device name and UUID:
    Code:
    ARRAY /dev/md0 UUID=e4665ceb:15f8e4b6:b186d497:7d365254
    And there seems to be some change to do with /dev/md/* and /dev/md* which I don't yet understand.


    2) You need to update initramfs so it contains your mdadm.conf settings during boot.
    Code:
    sudo update-initramfs -u
    Try those and report back.
    ASRock P67 Extreme6, Intel i5 2500K, 8GB RAM, nVidia 6600GT, 4x1TB RAID1+0

  7. #7
    Join Date
    Oct 2006
    Location
    Ayrshire
    Beans
    39,908
    Distro
    Ubuntu Development Release

    Re: RAID starting at md127 instead of md0

    Old thread closed.

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