[ale] RAID mirror boot nightmare

[Bob Toxen]

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)