[ale] RAID mirror boot nightmare

[Phil Turmel]

Good morning Bob,

On 07/10/2012 01:33 AM, Bob Toxen wrote:
> Additional details on this miserable problem:
> 
> On Boot the kernel complains of:
> 
>   Creating root device
>   Mounting root filesystem
>   Mount: Could not find filesystem '/dev/root'
> 
> after talking about md0 apparently being created successful and lastly
> panics.

This suggests that something in your initrd doesn't match your system
any more.  Its assembling md0 when your mdadm.conf below specifies md1
and md4.

> /boot/grub/grub.conf entry  being booted:
> title CentOS-single-md4
> 	root (hd0,0)
> 	kernel /vmlinuz-2.6.18-308.4.1.el5 ro root=/dev/md4 md=4,/dev/sda6,/dev/sdb6 md=1,/dev/sda2,/dev/sdb2 md-mod.start_dirty_degraded=1 rhgb single noresume
> 	initrd /initrd-2.6.18-308.4.1.el5.img

You shouldn't need the md=n,/dev/... items in this list if your
mdadm.conf is correct in the initrd.

> /etc/mdadm.conf (heavily edited by me including switching from uuid to
> devices; I don't presently list swap as that is not critical and it
> fails before even thinking about swap):
> # mdadm.conf written out by anaconda
> DEVICE /dev/sda[26] /dev/sdb[26]
> MAILADDR root
> ARRAY /dev/md4 level=raid1 num-devices=2 devices=/dev/sda6,/dev/sdb6 auto=yes
> ARRAY /dev/md1 level=raid1 num-devices=2 devices=/dev/sda2,/dev/sdb2 auto=yes

I've had the best success when the ARRAY lines have only the md node and
the uuid.

> fdisk output:
> Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
> 255 heads, 63 sectors/track, 121601 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1   *           1          13      104391   83  Linux
> /dev/sda2   *          14          26      104422+  fd  Linux raid autodetect
> /dev/sda3              27        4200    33527655   82  Linux swap / Solaris
> /dev/sda4            4201      121601   943023532+   f  W95 Ext'd (LBA)
> /dev/sda5            4201       62900   471507718+  83  Linux
> /dev/sda6           62901      121600   471507718+  fd  Linux raid autodetect
> 
> /etc/fstab:
> /dev/md4        /                       ext3    defaults        1 2
> /dev/md1        /boot                   ext3    defaults        1 2
> 
> #normal /dev/md3        /                       ext3    defaults        1 1
> #normal /dev/md0        /boot                   ext3    defaults        1 2
> #normal /dev/md4        /root2                  ext3    defaults        1 2
> #normal /dev/md1        /boot2                  ext3    defaults        1 2
> tmpfs                   /dev/shm                tmpfs   defaults        0 0
> devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
> sysfs                   /sys                    sysfs   defaults        0 0
> proc                    /proc                   proc    defaults        0 0
> /dev/md2                swap                    swap    defaults        0 0
> 
> 
> What magic am I missing?  Please help!!!

Might be useful to show us the output of "mdadm -E /dev/sda[26]".

You might just need to run "update-initrd" or whatever the equivalent is
for CentOS 5.8.  You always need to do this when you rearrange your boot
devices.



Phil.