Below is the reply from Gregory Leblanc, maintainer of the Linux RAID HOWTO and
active in a few other important projects.
On Tue, 2002-11-19 at 23:09, Warren Togami wrote:
Holy crap... my friend is in some severe trouble with his linux software
RAID. Any ideas about what he can do?
Sure, a few notes below.
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: [luau] NFS ate my raid superblock
Date: 19 Nov 2002 15:46:33 -0800
[snip]
hardlock. So I booted again, and got a message to the effect of "invalid
superblock, please use 'root='". So this kind of sucked. I tried
Hmm, I think that means it said "invalid RAID superblock", which is bad,
but not incurable. It could also be a filesystem superblock, which I
know relatively little about fixing.
booting off an old mdk 8.2 cd I had lying around, but it couldn't
auto-load my software raid-0 array in order to fsck it. So I have two
questions:
1. Can I easily fix my problem by booting a resue CD/disk, creating a
propper /etc/raidtab, then running mkraid and fsck?
Probably, yes.
2. How does the system know what my raid array is. For instance, the
kernel can boot my raid array without reading /etc/raidtab, because /etc
is on the array. Certain modern distro CD's can figure out where my /
partition is, load up the raid array, and read it no problem, without
needing /etc. But I suppose they can't do this without a valid
The raid superblock contains some information on which disks are part of
the RAID array, as well as some other information. If the partitions
are set to type 'fd' (Linux RAID), then the Linux kernel will attempt to
autodetect the RAID array. You should also be able to manually start
the array, probably by just putting together a raidtab that looks the
same as the original. If you want a bit less pain, Neil Brown has some
alternatives to the raidtools which are much easier to use. I think
they're called 'mdadm' or something like that. This URL has the sources
(latest version appears to be 1.0.1)
http://www.cse.unsw.edu.au/~neilb/source/mdadm/
superblock. Can someone explain this process to me? Also, ext3 creates
redundant superblocks throughout the partition, right?
ext3 only creates redundant filesystem superblocks. That may or may not
have anything to do with the superblock troubles that you're having, the
error message wasn't quite complete enough to say for sure. Hope this
helps, ping the linux-RAID list if searching the list archives doesn't
turn up anything.
Greg
-- Gregory Leblanc <[EMAIL PROTECTED]>
