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Re: [linux-lvm] Recovering from a disaster...




Going for my RHCE in a few weeks... Always wondered:

1. Are there any gotchas in a corrupted LVM volume?  For example,
/root/vg is an LVM volume, and either the 1st superblock on /root/vg or
maybe the underlying /dev/sda1 partition or even /dev/md0 (assuming
/root/vg could be sitting on top of a software RAID device) is zero'ed
out.  How does one go about fixing it?  Will a simple fsck here work?
But in the above case, is fsck run against md0 or sda1?

Simple fix:


	Until Intel-based systems have a usable bios don't put your
	root/boot volume on LVM. Since the BIOS will not be upgraded
	until at least three weeks after pigs floss I'd strongly
	suggest avoiding the pratice altogether.

The main reason is that any glitch in the LVM system will
leave the system unbootable. The root volume is small enough
that it does not require LVM for either performance or multi-
PV distribution. Mirroring it will be better done at the
hardware level to avoid kernel glitches frying the mirror.

2. If one knows that /dev/md0 is in trouble (composed of /dev/sda1 and
/dev/sdb1), but /dev/sda1 is fine, can one, upon boot, simply change
LILO/GRUB from trying to mount root from /dev/md0 to /dev/sda1?  My guess
is no, since the disk label is different.

A typical scnerario could be LVM sitting on top of MD, and have to
recover from some kind of disaster.  I wonder if the RedHat 8.0 rescue
option has all the modules/tools to repair such a disaster.

They don't support LVM out of the box, so this is unlikely.



-- Steven Lembark 2930 W. Palmer Workhorse Computing Chicago, IL 60647 +1 800 762 1582



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