HighMem

If you use software raid (md) and have a fakeraid controller (controlled by dm-raid), make sure to *never* install dmraid. It will kill your data.

There seem to be the kernel command line parameters preventing data loss...
noacpi nodmraid

https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/442735
http://mindspill.net/computing/linux-notes/mdadm-started-with-1-drive-out-of-2/