[ale] RAID mirror boot nightmare
Bob Toxen
transam at VerySecureLinux.com
Tue Jul 10 01:33:32 EDT 2012
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.
/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
/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
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!!!
Bob
On Mon, Jul 09, 2012 at 06:21:43PM -0400, Bob Toxen wrote:
> I'm having problems getting my RAID mirror booting again in
> CentOS 5.8 64-bit after GNU's gparted trashed my partition table when
> one of the new Seagate 1 TB SATA disks failed completely.
>
> Booting causes the kernel to complain of an invalid root partition.
> I can't figure out what is invalid about it. FSCK is happy.
>
> I rebuilt the partition table with "CD Rescue" v2.7.1 bootable CD
> (wonderful stuff) and reinstalled my existing GRUB to the MBR.
>
>
> Unfortunately, CentOS 5.8 will no longer recognize my md3 root partition
> (still running in degrated mode since I've not yet replaced the failed
> disk). The CentOS kernel does see the RAID partitions but just doesn't
> want to use one for /!!!
>
> I CAN boot the "CD Rescue" disk and tell it to find and boot an
> existing OS on the hard disk and it will bring up my CentOS 5.8 on
> md3 (before I did mdadm -S /dev/md3 and used fdisk to change its
> partition type from RAID to Linux)
> or will boot up md4 (though apparently with a newer 3.x kernel from the CD).
>
> However, no matter what I do I cannot get my CentOS 5.8 to boot the RAID
> mirror. I also have the root and /boot file systems duplicated to
> md4 and md1 respectively.
>
> I tried
>
> mdadm -S /dev/md3
> mdadm -S /dev/md1
> mdadm --create -n 2 /dev/md3 --level=mirror /dev/sda6 missing
> "/dev/sd6 appears to be part of an existing RAID; do anyway" y
> mdadm --create -n 2 /dev/md1 --level=mirror /dev/sda2 missing
> "/dev/sd2 appears to be part of an existing RAID; do anyway" y
>
> but when I try to boot CentOS 5.8 with "root-md3" it again fails.
>
> However, booting the CD Rescue and selecting "find and boot from hard
> disk" happily boots either RAID partition.
>
>
> Please PLEASE give me some ideas to fix this. $50 to the first right
> answer, REALLY! I'm desperate.
>
> Nothing on the file systems themselves, including the /boot/initrd*
> file and kernels, appear to be damaged. systems themselves)
>
>
> Since FSCK is happy all I can think of is damage to the md superblock at
> the end of the physical partitions. I wonder if the CD Rescue kernel
> (being newer than the CentOS kernel) created to new a version of the
> mdsuperblock. However, my recreating the RAID mirror under CentOS 5.8
> should have fixed it, shouldn't it?
>
> HELP! $50 prize. Really!
>
> Bob Toxen
> bob at VerySecureLinux.com
> transam at VerySecureLinux.com
> 404-216-5100 Cell (except for the next half hour)
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