Lab 17.1 Creating Software Raid - mdadm: RUN_ARRAY failed: Invalid argument

ultraninja

I'm using the LFS Ubuntu 14.1 lab VM.

Basically, I added an additional 1GB virtual drive to the VM in Virtualbox. Partitioned it with fdisk.

pvcreate /dev/sdb1

vgcreate VG /dev/sdb1

lvcreate -L 200M -n MD1 VG

lvcreate -L 200M -n MD2 VG

root@ubuntu:/home/student# lvdisplay
--- Logical volume ---
LV Path /dev/VG/MD1
LV Name MD1
VG Name VG
LV UUID BVR2X8-jltC-MCSd-WulR-2IXQ-uc7c-6SEjvr
LV Write Access read/write
LV Creation host, time ubuntu, 2015-12-28 15:16:00 -0600
LV Status available
# open 0
LV Size 200.00 MiB
Current LE 50
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 252:0

--- Logical volume ---
LV Path /dev/VG/MD2
LV Name MD2
VG Name VG
LV UUID A8P9JO-RKwK-XlUB-Ifw7-mrtI-yfFO-zV3lQY
LV Write Access read/write
LV Creation host, time ubuntu, 2015-12-28 15:16:03 -0600
LV Status available
# open 0
LV Size 200.00 MiB
Current LE 50
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 252:1

root@ubuntu:/home/student# mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 /dev/VG/MD1 /dev/VG/MD2
mdadm: Note: this array has metadata at the start and
may not be suitable as a boot device. If you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
mdadm: size set to 204608K
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: RUN_ARRAY failed: Invalid argument

root@ubuntu:/home/student# cat /proc/mdstat
Personalities :
unused devices: <none>

I've also tried adding 2x 1GB virtual disks in Virtualbox, then trying to create a raid array with those 2 disks. Same error "mdadm: RUN_ARRAY failed: Invalid argument"

After battling with this for a few hours, reading man pages, and googling, I'm still getting the error.

coop

What kernel are you running? If you are running the custom kernel on the LF VM,
it is likely not configured for RAID properly; it is intended for *this course* that you use the stock distro kernel. (the custom kernels are for use in kernel devel courses)
Check uname -r ; if it is reporting 4.3.0 or whatever, you are probably toast.

If you are using the Ubuntu stock kernel (choose at boot time) you should be ok.
Check if CONFIG_MD_RAID* is set (look at /boot/config*)

If this is not the problem, let us know/

ultraninja

Thanks for the reply. Yup, it was the kernel. I just installed the generic kernel from the repositories. I have 2 remaining questions:
1) How can I check if RAID is supported in a booted kernel?

root@ubuntu:/boot# grep RAID config-`uname -r`
CONFIG_RAID_ATTRS=m
CONFIG_BLK_DEV_3W_XXXX_RAID=m
CONFIG_SCSI_AACRAID=m
CONFIG_MEGARAID_NEWGEN=y
CONFIG_MEGARAID_MM=m
CONFIG_MEGARAID_MAILBOX=m
CONFIG_MEGARAID_LEGACY=m
CONFIG_MEGARAID_SAS=m
CONFIG_SCSI_PMCRAID=m
CONFIG_MD_RAID0=m
CONFIG_MD_RAID1=m
CONFIG_MD_RAID10=m
CONFIG_MD_RAID456=m
CONFIG_DM_RAID=m
CONFIG_DMA_ENGINE_RAID=y
CONFIG_ASYNC_RAID6_TEST=m
CONFIG_ASYNC_RAID6_RECOV=m
CONFIG_RAID6_PQ=m

root@ubuntu:/boot# grep RAID config-4.2.0 
# CONFIG_RAID_ATTRS is not set
# CONFIG_BLK_DEV_3W_XXXX_RAID is not set
# CONFIG_SCSI_AACRAID is not set
# CONFIG_MEGARAID_NEWGEN is not set
# CONFIG_MEGARAID_LEGACY is not set
# CONFIG_MEGARAID_SAS is not set
# CONFIG_SCSI_PMCRAID is not set
# CONFIG_MD_RAID0 is not set
# CONFIG_MD_RAID1 is not set
# CONFIG_MD_RAID10 is not set
# CONFIG_MD_RAID456 is not set
# CONFIG_DM_RAID is not set
CONFIG_RAID6_PQ=m

I'm assuming the "is not set" values indicate the kernel wasn't compiled with RAID support on the 4.2 kernel. Oh, and the # commented out RAID lines.

2) I created the raid array with mdadm --create /dev/md0 --level=1 --raid-disks=2 /dev/sda3 /dev/sda4 yet when I check the array it's actually /dev/md127. I'm not sure why its md127 rather than md0. Maybe my mdadm.conf isn't correct.

student@ubuntu:~$ sudo fdisk -l

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders, total 83886080 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000045d1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048    37750783    18874368   83  Linux
/dev/sda2        37752830    41940991     2094081    5  Extended
/dev/sda3        41940992    42350591      204800   83  Linux
/dev/sda4        42350592    42760191      204800   83  Linux
/dev/sda5        37752832    41940991     2094080   82  Linux swap / Solaris

Disk /dev/md127: 209 MB, 209518592 bytes
2 heads, 4 sectors/track, 51152 cylinders, total 409216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/md127 doesn't contain a valid partition table

root@ubuntu:/home/student# cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md127 : active (auto-read-only) raid1 sda3[0] sda4[1]
      204608 blocks super 1.2 [2/2] [UU]
      
unused devices: <none>

Thanks for the help

luisviveropena

Hi,

You can check if the md support is included in the kernel config file. So just do:

grep _MD_ /boot/config-`uname -r`

It uses to be included as modules.

Happy new year!
Luis.

ultraninja

The reason I was getting /dev/md127 rather than /dev/md0:

Ubuntu Forums - RAID starting at md127 instead of md0

1: mdadm.conf needed to be edited to remove the --name directive.
For example:

ARRAY /dev/md0 UUID=e4665ceb:15f8e4b6:b186d497:7d365254

2: You need to update initramfs so it contains your mdadm.conf settings during boot.

sudo update-initramfs -u

Looks good now:

root@LFS-VirtualBox:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Thu Jan 21 14:27:14 2016
     Raid Level : raid1
     Array Size : 204608 (199.85 MiB 209.52 MB)
  Used Dev Size : 204608 (199.85 MiB 209.52 MB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Thu Jan 21 15:32:57 2016
          State : clean 
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : LFS-VirtualBox:0  (local to host LFS-VirtualBox)
           UUID : 8b25d1ce:4b396710:01d76fec:b0ba507d
         Events : 32

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       18        1      active sync   /dev/sdb2
root@LFS-VirtualBox:~# cat /proc/mdstat 
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid1 sdb2[1] sdb1[0]
      204608 blocks super 1.2 [2/2] [UU]
      
unused devices: <none>

luisviveropena

I'm glad to know that you solved it!

Regards,
Luis.