Comment 2 for bug 70085

I don't have a fix, but as a work-around you could prevent the menu.lst from being broken by adjusting the values the post*_hook lines in your /etc/kernel-image.conf which will prevent update-grub from running. You could also put the linux-image packages on hold. Then you only update the kernel manually, and you must remember to fix your menu.lst.

I don't know if it makes sense to try to make update-grub do anything about this. I suspect that most people really needing the high availability have a hardware-based RAID controller.

If you need raid on the boot drive and you don't have hardware RAID, then you may need to accept either holding the kernel, disabling automatic updating of the menu.lst, or simply accepting that you would need to visit the console and manually select something of the grub menu if one of your drive fails. After all, if you don't have a hardware-based raid, and the default drive fails aren't you going to have to go to console anyway to select select the other drive in the cmos settings to boot from?