s/w raid and bios renumbering HDs

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Date: Sun, 30 Oct 2005 23:34:04 -0800
To: debian-user@lists.debian.org

Hi,

I am trying to setup a RAID-1 setup for the boot/root partition. I got
the setup working, except what I see with some of my tests leave me
less convinced that it is actually working. I am not using the
raid-setup options in the debian installer, I am trying to add raid-1
to an existing system (followed
http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html -- 7.4 method 2)

I have /dev/hda (master on primary) and /dev/hdc (master on secondary)
setup as mirrors. I also have a cdrom on /dev/hdd. Now if I disconnect
hda and reboot, everything seems work work - except what used to be
/dev/hdc comes up as /dev/hda. I know this since I the bios does
complain that "primary disk 0" is missing and I would have expected a
missing hda, not a missing hdc. Anyways, the software seems to
recognize the "failed-disk" fine if I connect the real hda back. Is
this the way it is supposed to work? Can I rely on this? Also what
happens when I move on to fancier setups like raid5?. My box is a dell
400sc with some phoenix bios (doesnt have many options either). I get
different (still unexpected) results with the cdrom connected and not.

Question #2 (probably related to my problem)

My grub menu.lst is as follows (/dev/md0 is made of /dev/hda1 and /dev/hdc1)
For testing, I made two entries (one for (hd0,0) and another for
(hd1,0)). The howto
I was reading wasn't clear to me. Should I be making just one entry
pointing to /dev/md0?
Also trying labels for "hda" and "hdc" after connecting the faulty
drive back gave me different results ( in one case I was looking at
"older" data and in the other case I wasn't)

(ignore the vs2.1.xxx. it is a linux-vserver patch - shouldn't matter here)

title Debian GNU/Linux, kernel 2.6.13.3-vs2.1.0-rc4-RAID-hda
root (hd0,0)
kernel /boot/vmlinuz-2.6.13.3-vs2.1.0-rc4 root=/dev/md0 ro
initrd /boot/initrd.img-2.6.13.3-vs2.1.0-rc4.md0
savedefault
boot

title Debian GNU/Linux, kernel 2.6.13.3-vs2.1.0-rc4-RAID-hdc
root (hd1,0)
kernel /boot/vmlinuz-2.6.13.3-vs2.1.0-rc4 root=/dev/md0 ro
initrd /boot/initrd.img-2.6.13.3-vs2.1.0-rc4.md0
savedefault
boot

Any help is appreciated. If there is a better/current HOWTO, please
let me know. The ones I have seen so far refer to now deprecated tools
(raidtools or raidtools2) and I have had a hard time trying to find
the equivalent syntax for mdadm.

--
Hari

• Previous message: Michael Rozhavsky: "Re: Stock vs. Debian kernel sources"
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