There needs to be a method to install Debian onto a software RAID mirror. This has been lacking for years it seems. Others have figured it out, why hasn't Debian?
Tools like mdadm and raidtools2 are out there. However the current kernel-images don't even support having "/" on a ["RAID1"] mirror.
Only inclusion of the mdadm package and the corresponding kernel options would be enough for me...
The above comments are both correct.
To fix this, the first step would be to include the Software Raid into a bootable kernel. This could even be a seperate kernel on the boot CD, as to not interfere with the existing install kernel. Call it 'kernel-raid' or something simular. Also, the raidtools2 or mdadm utilties would have to be included. Finally, the installer would have to know how to create a raid drive, much like it makes a lvm disk. Finally, the installer would have to install the raid version of the kernel in place of the non-raid kernel.
A series of raid-enabled kernels in the default repositories would be nice as well.
Remember, Debian's competition is already doing this. That might not be enough for some developers to work on this, but then again it might be just the motivation needed for others.
I'm not sure about how official this is. But personally I have installed Sarge from scratch on the 12th of October 2004 (testing, installer+Base CD iso) and am pleased to be able to tell you that installing on ["RAID1"] did Just Work(TM). The installation boots a initrd kernel and assembles (using mdadm) the raid devices for my root partition and swap partition in the initrd using modules, thus not needing different kernels. It even works so good that I haven't bothered yet recompiling my own kernel yet. Although I will do that eventually anyway.
About the previous comment: This is because the stock kernel-image packages have the necessary modules in initrd. The rootraiddoc debian documentation says that for raid modules to load through initrd with a / raid volume, the initrd kernel should boot from a non-raid volume. This doesn't seem to be the case, however - it looks like grub can pull the initrd.img at boot time from a raid volume anyway...