RE: software mirroring of boot drive

["Grunloh, Robert" <grunlohr u library arizona edu>]

Thanks Ed, Joshua, and Daryl. I'm in a catch-22 I think.

grub-install /dev/sdb
gives "/dev/sdb does not have any corresponding bios drive".

however fdisk -l /dev/sdb gives normal output (partition type ID = fd, and
first (/boot) partition flagged active for good luck.)

raidstop -a
gives "/dev/md0: device or resource busy" and same for md1.

This also is the case in single-user mode, and using mdadm --stop /dev/md0
gives the same busy message.

Then I tried Daryl's suggestion and ran the grub shell. however it couldn't
find sd0 or sd1, and pressing tab gave no choices.  This was while running,
as opposed to bootup, which was probably my mistake, because upon rebooting
grub can't find stage2. So I guess I finally got things unmirrored ;-)  I
might try again after a reinstall (no data lost).

It looks like even if I get this working it should be with lilo. But so far
software raid on the boot drive still doesn't look like a good practice to
me if I can try for an alternative.

thanks again
Robert Grunloh

-----Original Message-----
From: Ed Wilts [mailto:ewilts ewilts org] 
Sent: Friday, June 25, 2004 10:14 AM
To: Discussion of Red Hat Enterprise Linux 3 (Taroon)
Subject: Re: software mirroring of boot drive


On Fri, Jun 25, 2004 at 09:16:52AM -0700, Grunloh, Robert wrote:
> I'm trying to set up a rhel 3 server with 2 18gig scsi drives, where 
> each disk has the entire os and mirrors the other, so that we have no 
> downtime if either drive fails. The machine doesn't have hardware 
> raid, so I've partitioned it as sda1 & sdb1 /boot and sda2 & sdb2 /  
> and then created md0 and md1 during the install (raid 1). From what I 
> can tell everything is working once booted.
> 
> However if, as a test, I tell the scsi card's bios to boot off of the 
> 2nd drive it just hangs (no errors) before the grub menu appears. Same 
> behavior if I unplug the first drive. If I unplug the 2nd drive it 
> boots ok but complains about degraded mode, as expected.
> 
> I suspect the partitions are mirrored but grub isn't properly 
> installed on the second drive's MBR or isn't aware of it. However I 
> can't seem to unmirror them to work on the problem, since they're in 
> use, not that I'm good with grub anyway. -- I must be missing 
> something obvious.

I haven't tested it, but I would try:

# grub-install /dev/sdb

Disclaimer:  I meant it - I haven't tried it, and if you break your system,
you get to keep both pieces...

-- 
Ed Wilts, RHCE
Mounds View, MN, USA
mailto:ewilts ewilts org
Member #1, Red Hat Community Ambassador Program


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