software mirroring of boot drive

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

Hi,

you all were so good at answering my last beginner question, I have another.
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.

This isn't a config I'm especially in favor of, but I've been assigned to
get it working if possible. Can anyone point me to some howtos or faqs? I've
searched but found only older docs for lilo, and a nice IBM article covering
pservers. This box is a dell PE2500, but I'm testing now on a generic old pc
with adaptec card.

thanks much
Robert Grunloh
University of Arizona Library

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"Very few of us know how much we have to know in order to know how little we
know."