Comment 1 for bug 220493

I can confirm this--Nvidia fakeraid 5; using the kubuntu x86-64 release install, the dm-raid4-5 module is present and appears to load successfully on modprobe. It reports itself as loaded, but otherwise has no effect. There is no dmesg output, 'dmsetup targets' does not list the raid45 target type, and 'dmraid -ay' fails with the above error. The beta with 2.6.24-12 kernel will happily activate and mount the RAID using the supplied dm-raid4-5.

My plan is to compile a new 2.6.24-16 kernel and dm-raid4-5 module from source and see if that works, but I won't get the chance for another couple of days.