Lenny (5.0) and later support having the root and /boot partition on RAID volume. Actually, you can have root on RAID1+LVM partition.
This page contains some screenshots to demonstrate it, and applies to Debian 5.0 through, at least, 8.0, and probably 11.0.
Root on software RAID+LVM
In this example, we use virtual machine (qemu or kvm)... we can play, and break them 
$ sudo apt-get install kvm $ qemu-img create -f qcow2 hda.qcow2 4G Formatting 'hda.qcow2', fmt=qcow2, size=4194304 kB $ qemu-img create -f qcow2 hdb.qcow2 4G Formatting 'hdb.qcow2', fmt=qcow2, size=4194304 kB $ kvm -hda hda.qcow2 -hdb hdb.qcow2 -cdrom debian-lenny-i386-netinst.iso -boot d
Of course, you need to download a cdrom image.
Root on RAID+LVM example
Those few screenshots show how to install root on lvm on raid :
Once you have reach DebianInstaller partitioning screen...
Choose manual partitioning, then on each disk, manually create a partition (same size on both disks).
Create partitions for RAID
Use as "Physical volume for Raid" :
Configure RAID
We have a raid partition on each disk:
Choose the type of multidisk device to be created:
We have two partition:
- (In this example, we have no spare partition).
Let's select the partitions to use:
That's it !
Configure LVM
Let's configure the Logical volume manager:
First create a volume group:
Here, I chose the name vg1 for the group:
We have only one raid device:
Let's create the logical volume (kind pf partitions):
Our Logical volume (LV) will use some disk space from vg1 (which belongs to md0):
I named my partition foobar_root:
In this example, we wont split the filesystem (we won't even bother to create a swap, which is a bad idea), so I use all the disk space. (which again isn't a good idea, since it's so easy ro resize a partition with LVM)
Finish:
Use the LVM volumes
Let's assign and format the volumes (partitions):
As usually...
Done!
Install the bootloader (GRUB)
In Jessie (8.0), and I believe Wheezy (7.0), the installer will install GRUB even on RAID installs. However, GRUB can not install to a RAID device (e.g., /dev/md0), but will nonetheless work fine.
When you install in UEFI mode, refer to RAID for the EFI System Partition as the following steps only work for BIOS mode.
When asked to install bootloader, install to first device:
After first boot, consider executing dpkg-reconfigure grub-pc, and install to all devices. This way, your system will still boot correctly even if you reorder your drives.
Reboot Debian
Debian is booting:
See also
Recover a DegradedArray RAID array
http://lists.debian.org/debian-user/2008/10/msg01989.html
CategoryDebianInstaller | CategoryRoot | CategoryHardware | CategorySystemAdministration | CategoryRedundant: merge with other ?CategoryRaid pages