Comment 52 for bug 290885

I've walked through the steps at http://wiki.ubuntu.com/BootDegradedRaid and can confirm that the degraded raid boot options work (modulo the issue I raised around grub/MBR). The dpkg-reconfigure steps, the kernel command line options, and the /etc/initramfs/conf.d/mdadm settings all seem to work correctly. After I ran the grub-install, I was able to boot in degraded mode or not, depending on configuration, to either disk in the raid setup. I was able to re-add partitions back into the degraded arrays with mdadm, as well as fail, remove, and reconfigure devices. I didn't notice any regressions.

My testing was in an virtualbox vm so I was unable to hot-add an entire disk to emulate step 13 in the wiki page.