raid1 bootable disks
I did'nt check my raid1 last May, at the time of a hot discussion on this list
about bootable disks with raid1. I was busy to put mpqc at work. Now that it
works beautifully - and I understand I can invest on it - I begin to be
concerned with security issues. That so much because yesterday my window
manager jwm hanged during a four-days mpqc issue, while mpqc was still
running. It is wrong to start X and windows managers for computation sessions
but I did the mistake (I just wanted to check the cpu temp, and I never
learned properly how to switch beteewen consoles with [Alt]+F2 without a
With debian am64, two SATA disks, ext3 filesystem throughout, grub is on its
own partition /boot.
I took some notes from last May and I wonder where to turn now my attention
To enable booting from all disks in the RAID, you just need
to run 'grub-install /dev/xxy' where xxy is, e.g. hdb or sdb,
depending on your system, after you installed grub within d-i.
Or, as written in the Software-RAID HOWTO: call grub and type:
grub>device (hd0) /dev/xxy
I run grub-install /dev/sda and /dev/sdb, and both disks are perfectly
bootable. I have tested this.
grub-install seems to have issues with seperate boot partitions. If you
create a symlink inside boot called boot pointing to itself, then
grub-install is fine with it.
cd /boot; ln -s . boot
With that there is no problem with grub on raid1 /boot.
You have to trick grub-install. Say /boot is on /dev/md0, a raid1 of
/dev/sda1 and /dev/sdb1. Then you can put /dev/sda1 into devices.map,
instal-grub, repeat for sdb1. You might have to change fstab and/or
mtab as well. Can't remeber if that is truely needed.
But grub-install also has some special code for raids. Why it doesn't
work or isn't good enough should be someones TODO. Maybe we could make
that a NM job
By setting up each device in
device.map in turn you get grub on each of them.
If a disk fails the system should keep running. Thats the point of
raid after all. So when you do reboot it will usualy be to replace the
disk. So I'm not much concerned if the system is still bootable with a
broken disk still connected. It is likely the bios won't like that at
all no matter what the MBR looks like.
Hope not to have misrepresented the suggestions by cutting parts of the
Thanks a lot for your attention