[lug] SW Raid question

[Hugh Brown]

> I guess I'm confused. It seems that you are saying that the block addresses
> that get written into the mbr have some kind of device specifier. I have 
> moved
> a disk from sdb to sda where sdb was prepped using root (hd1,0) in grub.
> Booted the former sdb in the sda position just fine with only the one disk.
> Didn't even appear to look for an sdb device. I did adjust the root 
> statement
> in grub.conf to (hd0,0), but did nothing to any device lines.


Currently the vote is 2 against 1. :)  I suspect I'll learn something. 
I've got a CentOS 4.4 minimal image installed now w/ /boot on /dev/md0 
(which is /dev/sda1 and /dev/sdb1) and everything else in a volume group.

I've copied off the first 512 bytes of sda and sdb after the install. 
I'm snapshotting now.  After that, I'll turn off the VM, disable sda and 
check to see if it boots.

Next, I'll re-enable sda, boot, do the example with
device (hd0) /dev/sdb

dd off the first 512 bytes of sda and sdb, shutdown, disable sda and see 
if it boots

Next, I'll revert to the snapshot, do the setup (hd1,0) version of the 
example, dd off the first 512 byes of sda and sdb, disable sda and see 
if it boots.

Finally, I'll diff the two boot sectors for sdb between the two examples.

Sound like a reasonable test?

Hugh