At Fri, 8 Jan 2010 22:40:21 -0500 CentOS mailing list centos@centos.org wrote:
My CentOS4 machine died (CPU cooler failure, causing CPU to die). In this machine I had 5 Tbyte disks in a RAID5, and LVM structures on that.
Now I've moved those 5 disks onto a CentOS5 machine and the RAID array is being rebuilt. However the LVM structures weren't detected at boot time. I was able to "vgscan" and 'vgchange -a y' to bring the volume online and then fsck the logical volumes.
But I was concerned this didn't happen at boot time. Do I need to do anything else, or have the commands I've run done sufficient?
FWIW, this machine has no other LVM (nor RAID) disks on it.
This is why. Unless the machine 'knows' to look for LVM (eg has the mumble mumble in /etc/lvm/), it wouldn't look for it during start up. And unless it's root file system is on LVM its initrd won't have the "vgscan" and 'vgchange -a y' commands in the init script.
RAID itself is seen by the kernel if the disks are partitioned with 'Linux RAID Autodetect' partition types.
(only 5 more hours for the rebuild to complete!)
And hopefully, you won't get a disk error in the those errors and lose the whole array.