software raid

David Woyciesjes woyciesjes at
Wed Mar 22 18:08:30 UTC 2006

Carl Karsten wrote:

> I have been messing around with software raid1 - mirroring 2 drives - 
> including the boot sectors. The goal is to be able to remove either 
> drive and still have a functioning system.
> I realize that this is "not supported" given that "Add support for 
> software RAID." is on the but I have 
> heard it can be done with some trickery: install grub on both drives and 
> rely on the fact that /dev/hda1 and /dev/hda2 and /dev/md0 are all "the 
> same thing" as long as md0 is the only one that gets written to.
> But I did run into one problem:  if you have ide master and slave, and 
> you pull the master, the slave dissapears and the box/bios won't see it 
> so it won't boot from it.  so I am guessing I have to make each drive 
> the master on a seperate ide bus so that pulling one won't take out the 
> other.
> Before I spend too much time trying to make this work, anyone know of a 
> HowTo that outlines this?
> CarlFK

	Well, I followed the instructions here...
... with more detail here...
...when I installed my Edubuntu server. Here's the setup I have:
md0 - raid1 17GB / partition - hda1, hdc1
md1 - raid5 80GB /home partition - hda2, hdb1, hdc2
md2 - raid 1 3GB(?) swap partition - hda3, hdc3

Pri. IDE-
hda 60GB
hdb 40GB
Sec. IDE -
hdc 80GB
hdd (CD drive)

	Yes, I know I should have each drive on it's own IDE channel. Anybody 
got a PCI IDE controller they can spare? ;-)

	As for whether on not the raid1 boot setup works, I checked last night....
	First, I yanked both drives on the primary channel. Got a grub error 
15. First, I need to research what that means, and second, I need figure 
out the right way to put lilo on to replace grub.
	According to the LVMOnRaid wiki page, lilo should've been automatically 
installed, but it wasn't. Maybe something to do with the Edubuntu 
installer vs. the Breezy installer. Probably would've caught this if I 
did an expert install.
	Then I yanked the secondary IDE channel. Edubuntu booted up fine 
without hdc there.

	Hmm, after just a little Google time, I found this page...
(also -
...which just might be the answer I need about the grub error 15.

--- Dave Woyciesjes
--- ICQ# 905818
--- AIM - woyciesjes

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